Filed Pursuant to Rule 424(b)(5)
Registration No. 333-277002

The information in this preliminary prospectus supplement is not complete and may be changed. This preliminary prospectus supplement and the accompanying prospectus are part of an effective registration statement filed with the Securities and Exchange Commission. This preliminary prospectus supplement and the accompanying prospectus are not an offer to sell these securities and they are not soliciting an offer to buy these securities in any jurisdiction where the offer or sale is not permitted.

SUBJECT TO COMPLETION, DATED DECEMBER 9, 2024

PRELIMINARY PROSPECTUS SUPPLEMENT

To prospectus dated February 12, 2024

$    

Arthur J. Gallagher & Co.

$     % Senior Notes due 2027

$     % Senior Notes due 2029

$     % Senior Notes due 2032

$     % Senior Notes due 2035

$     % Senior Notes due 2055

Arthur J. Gallagher & Co. (the “Company”) will issue $   aggregate principal amount of senior notes that will mature on    , 2027 and bear interest at  % per annum (the “2027 Notes”), $   aggregate principal amount of senior notes that will mature on    , 2029 and bear interest at  % per annum (the “2029 Notes”), $   aggregate principal amount of senior notes that will mature on    , 2032 and bear interest at  % per annum (the “2032 Notes”), $   aggregate principal amount of senior notes that will mature on    , 2035 and bear interest at  % per annum (the “2035 Notes”) and $   aggregate principal amount of senior notes that will mature on    , 2055 and bear interest at  % per annum (the “2055 Notes” and, together with the 2027 Notes, the 2029 Notes, the 2032 Notes and the 2035 Notes, the “Notes”).

Interest on the Notes will accrue from    , 2024. Interest on the 2027 Notes and the 2029 Notes is payable semi-annually in arrears on    and     of each year, and the first interest payment date will be on    , 2025. Interest on the 2032 Notes, the 2035 Notes and the 2055 Notes is payable semi-annually in arrears on    and     of each year, and the first interest payment date will be on    , 2025.

The Notes will rank equally with all existing and future unsecured, unsubordinated indebtedness of the Company and will rank senior to any subordinated indebtedness that the Company may incur.

The Notes may be redeemed at the option of the Company in whole at any time or in part from time to time at the applicable redemption prices specified under “Description of Notes—Optional Redemption,” plus accrued and unpaid interest, if any, up to, but excluding, the redemption date. The Notes are also subject to a Special Optional Redemption described under “Description of Notes—Special Optional Redemption upon a Transaction Termination Event.”

As described under “Description of Notes—Purchase of Notes Upon a Change of Control Triggering Event,” if the Company experiences a change of control and a ratings decline, the Company will be required to offer to purchase the Notes from holders, unless the Company has previously redeemed the Notes.

Investing in our Notes involves risks. See “Risk Factors” beginning on page S-21 of this prospectus supplement and on page 3 of the accompanying prospectus. You should also consider the risk factors described in the documents incorporated by reference into this prospectus supplement and the accompanying prospectus, including the risk factors described in our Annual Report on Form 10-K for the fiscal year ended December 31, 2023.

Per 2027 Note

Total

Per 2029 Note

Total

Per 2032 Note

Total

Per 2035 Note

Total

Per 2055 Note

Total

Public offering price(1)

%

$

%

$

%

$

%

$

%

$

Underwriting discount

%

$

%

$

%

$

%

$

%

$

Proceeds to the Company (before expenses)

%

$

%

$

%

$

%

$

%

$

(1) Plus accrued interest from    , 2024, if settlement occurs after that date.

Neither the Securities and Exchange Commission (the “SEC”) nor any state securities commission has approved or disapproved of the securities or passed upon the accuracy or adequacy of this prospectus supplement or the accompanying prospectus. Any representation to the contrary is a criminal offense.

The Notes will be ready for delivery in book-entry form only through the facilities of The Depository Trust Company (“DTC”), for the accounts of its participants, including Euroclear Bank, SA/NV and Clearstream Banking, S.A. on or about    , 2024.

Joint Book-Running Managers

BofA Securities Morgan Stanley

The date of this prospectus supplement is     , 2024.

TABLE OF CONTENTS

Prospectus Supplement

	Page
ABOUT THIS PROSPECTUS SUPPLEMENT		S-ii
CAUTIONARY STATEMENTS REGARDING FORWARD-LOOKING STATEMENTS		S-iii
SUMMARY		S-1
THE OFFERING		S-3
UNAUDITED PRO FORMA CONDENSED COMBINED FINANCIAL INFORMATION		S-7
RISK FACTORS		S-21
USE OF PROCEEDS		S-26
DESCRIPTION OF NOTES		S-27
CERTAIN UNITED STATES FEDERAL INCOME TAX CONSEQUENCES		S-41
UNDERWRITING		S-45
LEGAL MATTERS		S-53
EXPERTS		S-53
WHERE YOU CAN FIND ADDITIONAL INFORMATION		S-53
INCORPORATION BY REFERENCE		S-53

Prospectus

	Page
ABOUT THIS PROSPECTUS		1
ARTHUR J. GALLAGHER & CO.		2
RISK FACTORS		3
CAUTIONARY STATEMENT REGARDING FORWARD-LOOKING STATEMENTS		4
USE OF PROCEEDS		8
SELLING SECURITYHOLDERS		9
DESCRIPTION OF SECURITIES		10
PLAN OF DISTRIBUTION		11
LEGAL MATTERS		12
EXPERTS		13
WHERE YOU CAN FIND MORE INFORMATION		14
INCORPORATION OF CERTAIN INFORMATION BY REFERENCE		15

You should rely only on the information contained in or incorporated by reference in this prospectus supplement, the accompanying prospectus or that is contained in any free writing prospectus prepared by us or on our behalf. We have not, and the underwriters have not, authorized any other person to provide you with different information. If anyone provides you with different or inconsistent information, you should not rely on it. We and the underwriters take no responsibility for, and can provide no assurances as to the reliability of, any other information that others may give you. We are not, and the underwriters are not, making an offer to sell the Notes in any jurisdiction where the offer or sale is not permitted. You should assume that the information appearing in this prospectus supplement and the accompanying prospectus and in the documents incorporated by reference herein and therein or that is contained in any free writing prospectus issued by us is accurate only as of their respective dates. Our business, financial condition, results of operation and prospects may have changed since those dates.

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ABOUT THIS PROSPECTUS SUPPLEMENT

We provide information to you about the Notes in two separate documents: (1) this prospectus supplement, which describes the specific terms of the Notes and also adds to and updates information contained in the accompanying prospectus and the documents incorporated by reference in that prospectus and (2) the accompanying prospectus, which provides general information about securities we may offer from time to time, including securities other than the Notes being offered by this prospectus supplement. If information in this prospectus supplement is inconsistent with the accompanying prospectus, you should rely on this prospectus supplement.

It is important for you to read and consider all of the information contained in this prospectus supplement and the accompanying prospectus in making your investment decision. You also should read and consider the information in the documents we have referred you to in “Where You Can Find Additional Information” in this prospectus supplement and the accompanying prospectus.

We include cross-references in this prospectus supplement and the accompanying prospectus to captions in these materials where you can find additional related discussions. The table of contents in this prospectus supplement provides the pages on which these captions are located.

Unless otherwise indicated or the context otherwise requires, references in this prospectus supplement to the “Company,” “Gallagher,” “we,” “our” and “us” refer to both Arthur J. Gallagher & Co. and its consolidated subsidiaries. The term “you” refers to a prospective investor.

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CAUTIONARY STATEMENTS REGARDING

FORWARD-LOOKING STATEMENTS

This prospectus supplement, the accompanying prospectus and the documents they incorporate by reference, contain certain statements related to future results, or state our intentions, beliefs and expectations or predictions for the future, which are forward-looking statements as that term is defined in the Private Securities Litigation Reform Act of 1995. Forward-looking statements relate to expectations or forecasts of future events and use words such as “anticipate,” “believe,” “estimate,” “expect,” “contemplate,” “forecast,” “project,” “intend,” “plan,” “potential” and other similar terms, and future or conditional tense verbs like “could,” “may,” “might,” “see,” “should,” “will” and “would.” You can also identify forward-looking statements by the fact that they do not relate strictly to historical or current facts. For example, we may use forward-looking statements when addressing topics such as: statements regarding expected benefits of the proposed Transaction (as defined in “Summary—Recent Developments”); the benefits of the proposed Transaction, including future financial and operating results and synergies; the expected revenue, earnings per share (“EPS”), net earnings before interest, income taxes, depreciation, amortization and the change in estimated acquisition earnout payables (“EBITDAC”) and credit rating impacts of the proposed Transaction; the size and status of the combined organization within various jurisdictions; required regulatory approvals; expected timing of completion of the proposed Transaction; expected duration and cost of integration, and the anticipated financing of the proposed Transaction; the plans, objectives, expectations and intentions with respect to the Acquired Entity; the impact of general economic conditions, including inflation, interest rates and market uncertainty; the effects of geopolitical volatility, including repercussions from the wars in Ukraine and the Middle East; market and industry conditions, including competitive and pricing trends and the impact of large natural events; acquisition strategy including the expected size of our acquisition program; the expected impact of acquisitions and dispositions; and integrating recent acquisitions, including the expected benefits of our acquisition of the Willis Towers Watson plc treaty reinsurance brokerage operations (“Willis Re”), BCHR Holdings, L.P., and its subsidiaries, dba Buck (“Buck”), Cadence Insurance, Inc. (“Cadence Insurance”), Eastern Insurance Group, LLC (“Eastern Insurance”), My Plan Manager Group Pty Ltd (“My Plan Manager”) and other acquisitions larger than our typical tuck-in acquisitions and the expected duration and costs of integrating such large acquisitions; the development and performance of our services and products; changes in the composition or level of our revenues or earnings; our cost structure and the size and outcome of cost-saving or restructuring initiatives; future capital expenditures; future debt levels and anticipated actions to be taken in connection with maturing debt; future debt-to-earnings ratios; the outcome of contingencies; dividend policy; pension obligations; cash flow and liquidity; capital structure and financial losses; future actions by regulators; the outcome of existing regulatory actions, audits, reviews or litigation; the impact of changes in accounting rules; financial markets; interest rates; foreign exchange rates; matters relating to our operations; income taxes; expectations regarding our investments; human capital management, including diversity and inclusion initiatives; sustainability matters, including climate- resilience products and services and carbon emissions; and integrating recent acquisitions. These forward-looking statements are subject to certain risks and uncertainties that could cause actual results to differ materially from either historical or anticipated results depending on a variety of factors.

Potential factors that could impact results include:

• Risks related to the integration of the operations, businesses and assets acquired in the proposed Transaction into the Company;

• The possibility that the proposed Transaction is not completed when expected or at all because required regulatory approvals are not received or other conditions to the closing are not satisfied on a timely basis or at all;

• The risk that our free cash generation is insufficient, or the financing required to fund the proposed Transaction is not obtained on the terms anticipated or at all;

• Potential adverse reactions or changes to business or employee relationships, including those resulting from the announcement or completion of the proposed Transaction;

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• The possibility that the anticipated benefits of the proposed Transaction, including cost savings and expected synergies, are not realized when expected or at all, including as a result of the impact of, or issues arising from, the integration of the acquired operations;

• Conditions imposed in order to obtain required regulatory approvals for the proposed Transaction;

• Uncertainties in the global economy and equity and credit markets and their potential impact on the Company’s ability to finance the proposed Transaction on acceptable terms, at favorable pricing, in a timely manner, or at all;

• The possibility that the proposed Transaction may be more expensive to complete than anticipated, including as a result of unexpected factors or events;

• Diversion of management’s attention from ongoing business operations and opportunities;

• The inability to retain certain key employees of the operations acquired in the proposed Transaction or the Company;

• Risks associated with increased leverage from the proposed Transaction;

• Competitive and market responses to the proposed Transaction;

• Uncertainties as to the timing of the consummation of the proposed Transaction and the ability of each party to consummate the proposed Transaction;

• That financial information subsequently presented for the business acquired in the proposed Transaction in our subsequent public filings may be different from that presented herein;

• Global economic and geopolitical events, such as fluctuations in interest and inflation rates; a recession or economic downturn; failures of financial institutions and other counterparties; a potential United States (U.S.) government shutdown or gridlock over increasing the U.S. debt ceiling; political violence and instability, including as a result of geo-economic fragmentation;

• Economic conditions that result in financial difficulties for underwriting enterprises or lead to reduced risk-taking capital capacity, for example, as a result of large payouts related to extreme weather events, or to the failure of such enterprises, including the increased risk of errors and omissions (which we refer to as E&O) claims against us;

• Risks that could negatively affect the success of our acquisition strategy, including the impact of economic uncertainty on our ability to source, review and price acquisitions; continuing consolidation in our industry and interest in acquiring insurance brokers on the part of private equity firms and newly public insurance brokers, which makes it more difficult to identify targets and in some cases makes them more expensive; inaccurate assumptions and failure to realize expected benefits; the risk that we may not receive timely regulatory approval of pending transactions; closing risks; execution risks; integration risks; poor cultural fit; the risk of post-acquisition deterioration leading to intangible asset impairment charges; and the risk we could incur or assume unanticipated liabilities such as cybersecurity issues or those relating to violations of anti-corruption and sanctions laws;

• Risks related to Willis Re, Buck, Cadence Insurance, Eastern Insurance, My Plan Manager and other acquisitions larger than our usual tuck-in acquisitions, including risks related to our ability to successfully integrate operations (including with respect to technology and financial systems required to be converted as transition services agreements phase out from time to time), the possibility that our assumptions may be inaccurate resulting in unforeseen obligations or liabilities and failure to realize the expected benefits of these acquisitions;

• Damage to our reputation, including as a result of sustainability matters, and the potential for the Internet and social media to magnify the effects of such reputational issues;

• Failure to meet our sustainability-related aspirations, goals and initiatives or to comply with increasingly complex climate-related regulations including increased risks related to “greenwashing”;

S-iv

• Emerging risks relating to the use of artificial intelligence (“AI”) in our business operations, including regulatory, data privacy and cybersecurity risks;

• Failure to apply technology, data analytics and AI effectively in driving value for our clients through technology-based solutions, or failure to gain internal efficiencies and effective internal controls through the application of technology and related tools;

• Risks associated with the use of AI in our business operations, including regulatory, data privacy, cybersecurity, E&O and competition risks;

• Failure to attract and retain experienced and qualified talent, including our senior management team, or adequately plan and execute for the succession of such leaders; increased costs resulting from increased compensation and benefits packages as a result of a tighter labor market, and negative effects from restrictions on non-compete agreements at the state level;

• A disaster or other significant disruption to business continuity for our own operations or those of third parties on which we rely, including cybersecurity incidents; natural disasters; political violence and unrest in the U.S. or elsewhere around the world; for example, our substantial operations in India could be negatively impacted as a result of the dispute between India and Pakistan involving the Kashmir region, rising tensions between India and China, incidents of terrorism in India, civil unrest or other reasons;

• Sustained increases in the cost of employee benefits and compensation expenses;

• Risks arising from our international operations and changes in international conditions, including the risks posed by political and economic uncertainty in certain countries (including repercussions from the wars in Ukraine and the Middle East), maintaining regulatory and legal compliance across multiple jurisdictions (such as those relating to violations of anti-corruption, sanctions and privacy laws, increasingly complex regulatory requirements related to climate change and sustainability issues and increased protectionism), tariffs, trade wars, climate change and other long-term sustainability matters and global health risks;

• Risks related to changes in U.S. or foreign tax laws, including a U.S. or foreign tax rate change, potential changes in guidance related to the U.S. Inflation Reduction Act, the Organisation for Economic Co-operation and Development’s (OECD) global minimum corporate tax regime, and other local policy changes;

• Competitive pressures, including as a result of innovation, in each of our businesses;

• Volatility or declines in premiums or other adverse trends in the insurance industry;

• The higher level of variability inherent in contingent and supplemental revenues versus standard commission revenues;

• Risks particular to our benefit consulting operations, including risks related to the acquisition of Buck;

• Risks particular to our third-party claims administrations operations, including risks related to the availability of RISX-FACS^®, our proprietary risk management information system, wage inflation, staffing shortages, any slowing of the trend toward outsourcing claims administration and the concentration of large amounts of revenue with certain clients;

• Climate risks, including the risk of a systemic economic crisis and disruptions to our business caused by the transition to a low-carbon economy;

• Cyber-attacks or other cybersecurity incidents and the heightened risk of such attacks as a result of the wars in Ukraine and the Middle East; improper disclosure of confidential, personal or proprietary data and changes to laws and regulations governing cybersecurity and data privacy;

• Unfavorable determinations related to contingencies and legal proceedings;

S-v

• Violations or alleged violations of the U.S. Foreign Corrupt Practices Act (which we refer to as FCPA), the United Kingdom (U.K.) Bribery Act 2010 or other anti-corruption laws and the Foreign Account Tax Compliance provisions of the Hiring Incentives to Restore Employment Act, and the outcome of any existing or future investigation, review, regulatory action or litigation;

• Failure to comply with regulatory requirements, including those related to governance and control requirements in particular jurisdictions, international sanctions, including new sanctions laws as a result of the wars in Ukraine and the Middle East; laws relating to the disclosure of sustainability-related matters; laws relating to the use of AI, or a change in regulations or enforcement policies that adversely affects our operations (for example, relating to insurance broker compensation methods or restrictions on non-compete agreements);

• Changes to our financial presentation from new accounting estimates and assumptions;

• Intellectual property risks;

• Risks related to our legacy clean energy investments, including intellectual property claims, environmental and product liability claims, environmental compliance costs and the risk of disallowance by the Internal Revenue Service of previously claimed tax credits;

• The risk that our outstanding debt adversely affects our financial flexibility and restrictions and limitations in the agreements and instruments governing our debt;

• The risk of credit rating downgrades;

• The risk that we may not be able to receive dividends or other distributions from our subsidiaries, including the effects of significant changes in foreign exchange rates;

• The risk of share ownership dilution when we issue common stock; and

• Volatility of the price of our common stock.

Forward-looking statements are not guarantees of future performance. They involve risks, uncertainties and assumptions, including the risk factors referred to above. Our future performance and actual results or outcomes may differ materially from those expressed in forward-looking statements. Accordingly, you should not place undue reliance on forward-looking statements, which speak only as of, and are based on information available to us on, the date of the applicable document. Many of the factors that will determine these results are beyond our ability to control or predict. All subsequent written and oral forward-looking statements attributable to us or any person acting on our behalf are expressly qualified in their entirety by the cautionary statements contained or referred to in this section. Forward-looking statements speak only as of the date that they are made, and we do not undertake any obligation to update any such statements or release publicly any revisions to these forward-looking statements to reflect events or circumstances after the date of this prospectus supplement or to reflect new information, future or unexpected events or otherwise, except as required by applicable law or regulation. In addition, historical, current and forward-looking sustainability-related statements may be based on standards for measuring progress that are still developing, internal controls and processes that continue to evolve and assumptions that are subject to change in the future.

A detailed discussion of the factors that could cause actual results to differ materially from our published expectations is contained under the heading “Risk Factors” below and in the accompanying prospectus and in our filings with the SEC, including our Annual Report on Form 10-K for the fiscal year ended December 31, 2023, and any reports we file with the SEC in the future, which are incorporated by reference to this prospectus supplement.

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SUMMARY

The following summary should be read together with the information contained in other parts of this prospectus supplement and the accompanying prospectus and the information incorporated by reference herein or therein. This summary highlights selected information from this prospectus supplement and the accompanying prospectus regarding the offering of the Notes. You should read this prospectus supplement and the accompanying prospectus, including the documents we incorporate by reference, carefully to understand fully the terms of the offering as well as other considerations that are important to you in making a decision to invest in the Notes. You should pay special attention to the “Risk Factors” section of this prospectus supplement and the accompanying prospectus, and the “Risk Factors” section in our Annual Report on Form 10-K for the fiscal year ended December 31, 2023, to determine whether an investment in the Notes is appropriate for you.

Our Company

We are engaged in providing insurance brokerage, reinsurance brokerage, consulting services, and third-party property/casualty claims settlement and administration services to entities and individuals around the world. In the nine-month period ended September 30, 2024, we generated approximately 65% of our revenues for the combined brokerage and risk management segments domestically and 35% internationally, primarily in Australia, Canada, New Zealand and the U.K. We have three reportable segments: brokerage, risk management and corporate. The brokerage and risk management segments contributed approximately 86% and 14%, respectively, to revenues during the nine-month period ended September 30, 2024. The corporate segment did not generate any significant revenues in the nine-month period ended September 30, 2024. Our major sources of operating revenues are commissions, fees and supplemental and contingent revenues from brokerage operations and fees from risk management operations. Interest income is earned on cash, cash equivalents and fiduciary cash and revenues are generated from premium financing.

Recent Developments

Transaction

On December 7, 2024, we entered into a Stock Purchase Agreement (the “Purchase Agreement”), by and among the Company, The AssuredPartners Group LP (the “Seller”) and Dolphin TopCo, Inc. (the “Acquired Entity”), pursuant to which the Company will acquire all of the issued and outstanding stock of the Acquired Entity for an aggregate purchase price of $13.45 billion in cash payable at closing, subject to certain customary adjustments as set forth in the Purchase Agreement (the “Transaction”). The Acquired Entity is the holding company of AssuredPartners, Inc., a Delaware corporation (together with its subsidiaries, “AssuredPartners”), a leading U.S. insurance broker with client capabilities across commercial property/casualty, specialty, employee benefits and personal lines and with operations in the U.K. and Ireland. The Acquired Entity’s revenues as reported were $2,222 million, $2,856 million and $2,556 million for the nine months ended September 30, 2024, the twelve months ended September 30, 2024 and the year ended December 31, 2023, respectively. The Acquired Entity’s pro forma Adjusted EBITDAC was $938 million for the twelve months ended September 30, 2024. Additionally, the Acquired Entity’s three-year average Organic Revenue growth rate was approximately 6%. The Company’s management applied certain adjustments to the Acquired Entity’s financial information to calculate the Acquired Entity’s pro forma Adjusted EBITDAC, including non-recurring legal, transaction-related, technology and acquisition-related compensation expense. See “Risk Factors—Certain financial information related to the Acquired Entity presented in this prospectus supplement is derived from financial statements that are not included herein and include certain non-GAAP measures and investors are cautioned not to place undue reliance on such information.”

The Purchase Agreement contains representations, warranties and covenants related to the Transaction that are customary for a transaction of this nature, and the completion of the Transaction is dependent upon receipt of

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regulatory clearances in the U.S., the U.K. and Ireland and certain other customary closing conditions. The Purchase Agreement includes customary termination provisions of the parties, including if (i) the closing of the Transaction has not occurred on or prior to March 9, 2026 (as may be extended to July 7, 2026 in certain circumstances, as further described in the Purchase Agreement), and (ii) the other party has materially breached its representations, warranties or covenants, subject to certain negotiated cure periods as set forth in the Purchase Agreement. The Company’s obligations under the Purchase Agreement are not conditioned on the receipt of financing.

The Purchase Agreement has been filed as an exhibit to the Company’s Current Report on Form 8-K, filed on December 9, 2024, and is incorporated by reference into this prospectus supplement to provide investors with information regarding its terms and conditions. It is not intended to provide any other factual information about the Company, the Seller or the Acquired Entity or any of their respective subsidiaries or affiliates. The representations, warranties and covenants contained in the Purchase Agreement were made only for purposes of that agreement and as of specific dates, were solely for the benefit of the parties to the Purchase Agreement, may be subject to limitations agreed upon by the contracting parties, including being qualified by confidential disclosures made for the purposes of allocating contractual risk between the parties to the Purchase Agreement instead of establishing these matters as facts, and may be subject to standards of materiality applicable to the contracting parties that differ from those applicable to investors. Investors in the Notes are not third-party beneficiaries under the Purchase Agreement and should not rely on the representations, warranties and covenants or any descriptions thereof as characterizations of the actual state of facts or condition of the Company, the Seller or the Acquired Entity or any of their respective subsidiaries or affiliates. Moreover, information concerning the subject matter of the representations and warranties may change after the date of the Purchase Agreement, which subsequent information may or may not be fully reflected in the Company’s public disclosures.

This Notes offering is not conditioned on the closing of the Transaction or the concurrent Common Stock Offering (defined below), and there can be no assurance that either the concurrent Common Stock Offering or the Transaction will be completed. See “Risk Factors—There can be no assurance that the Transaction will be completed or that we will realize the expected benefits of the Transaction.”

Concurrent Common Stock Offering

Concurrently with this offering, we are also making a public offering of $8.5 billion in shares of our common stock, $1.00 par value per share (“common stock”), pursuant to a separate registration statement (the “Common Stock Offering”). We have granted the underwriters of the Common Stock Offering a 30-day option to purchase up to an additional $1.275 billion in shares of our common stock. The closing of this Notes offering is not conditioned upon the closing of the Common Stock Offering, and the closing of the Common Stock Offering is not conditioned upon the closing of this Notes offering, so it is possible that this offering occurs and the Common Stock Offering does not occur, and vice versa. We cannot assure you that the Common Stock Offering will be completed on the terms described herein, or at all. Nothing contained herein shall constitute an offer to sell or a solicitation of an offer to buy our common stock. Certain of the underwriters of this offering are also underwriters in the Common Stock Offering.

See the section titled “Use of Proceeds” for additional information regarding the use of proceeds from the Common Stock Offering.

Corporate Information

Our principal executive offices are located at 2850 Golf Road, Rolling Meadows, Illinois 60008-4050. Our telephone number is (630) 773-3800. Our website is http://www.ajg.com. The contents of our website are not a part of this prospectus supplement or the accompanying prospectus.

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THE OFFERING

The following summary contains basic information about this offering. This summary is not intended to be complete. You should read the full text and more specific details contained elsewhere in this prospectus supplement and the accompanying prospectus. For a more complete description of the Notes, see “Description of Notes” in this prospectus supplement.

Issuer Arthur J. Gallagher & Co., a Delaware corporation.

Notes Offered $     aggregate principal amount 2027 Notes, $     aggregate principal amount 2029 Notes, $     aggregate principal amount of 2032 Notes, $     aggregate principal amount of 2035 Notes and $     aggregate principal amount of 2055 Notes.

Interest Rate The 2027 Notes will bear an interest rate equal to     % per annum, the 2029 Notes will bear an interest rate equal to     % per annum, the 2032 Notes will bear an interest rate equal to     % per annum, the 2035 Notes will bear an interest rate equal to     % per annum and the 2055 Notes will bear an interest rate equal to     % per annum.

Interest Payment Dates Interest on the 2027 Notes and the 2029 Notes is payable semi-annually in arrears on      and     of each year, beginning on , 2025 . Interest on the 2032 Notes, the 2035 Notes and the 2055 Notes is payable semi-annually in arrears on      and      of each year, beginning on     , 2025.

Maturity Date The 2027 Notes will mature on     , 2027, the 2029 Notes will mature on     , 2029, the 2032 Notes will mature on     , 2032, the 2035 Notes will mature on     , 2035 and the 2055 Notes will mature on     , 2055.

Ranking The Notes will be senior unsubordinated unsecured obligations of the Company and will:

• rank equally with all of the Company’s existing and future unsubordinated and unsecured debt;

• be senior in right of payment to all of the Company’s existing and future subordinated debt;

• be effectively subordinated to all of the Company’s existing and future secured debt, to the extent of the value of the assets securing such debt; and

• be structurally subordinated to all existing and future liabilities of the Company’s subsidiaries, including any claims of trade creditors.

As of September 30, 2024, we had approximately $4,550.0 million of outstanding senior indebtedness that would rank equally with the Notes. As of September 30, 2024, we had no secured indebtedness

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outstanding. The Company has only a stockholder’s claim on the assets of its subsidiaries. This stockholder’s claim is junior to the claims that creditors of such subsidiaries have against those subsidiaries. Holders of the Notes will be creditors only of the Company and not creditors of the Company’s subsidiaries. As a result, all the existing and future liabilities of the Company’s subsidiaries, including any claims of trade creditors, will be structurally senior to the Notes.

As of September 30, 2024, our subsidiaries had approximately $262.0 million of indebtedness (excluding intercompany liabilities) to which the Notes would have been structurally subordinated.

For more information on the ranking of the Notes, see “Description of Notes—Ranking.”

Optional Redemption Prior to the applicable Par Call Date (as defined below), we may redeem each series of Notes, in whole or in part, at any time and from time to time, at a redemption price equal to the greater of (1) (a) the sum of the present values of the remaining scheduled interest and principal payments on the Notes to be redeemed discounted to the redemption date (assuming the Notes matured on the applicable Par Call Date) as described in “Description of Notes—Optional Redemption,” less (b) interest accrued to the date of redemption; and (2) 100% of the principal amount of the Notes to be redeemed, plus accrued and unpaid interest, if any, to, but excluding, the redemption date. In addition, we may redeem the Notes of each series on or after the applicable Par Call Date, in whole at any time or in part from time to time, at a redemption price equal to 100% of the principal amount of the Notes redeemed plus accrued and unpaid interest, if any, to, but excluding, the redemption date.

For purposes of the foregoing, “Par Call Date” means     , 20  with respect to the 2027 Notes (the date that is months prior to the maturity date of such notes);     , 20  with respect to the 2029 Notes (the date that is      months prior to the maturity date of such notes);      , 20  with respect to the 2032 Notes (the date that is months prior to the maturity date of such notes);      , 20  with respect to the 2035 Notes (the date that is months prior to the maturity date of such notes); and      , 20  with respect to the 2055 Notes (the date that is months prior to the maturity date of such notes).

See “Description of Notes—Optional Redemption.”

Special Optional Redemption upon a Transaction Termination Event We may, at our option, redeem in whole, but not in part, any or all series of Notes by providing notice of such redemption to the holders of the series of Notes being redeemed within 30 days following a Transaction Termination Event (as defined herein), at a redemption

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price equal to 101% of the aggregate principal amount of the series of Notes being redeemed, plus accrued and unpaid interest, if any, to, but excluding, the redemption date.

If within 30 days after the occurrence of a Transaction Termination Event, we elect not to redeem a series of Notes, or if the Company notifies holders of its election to redeem a series of Notes within such 30-day period but does not consummate the redemption on the date fixed for such redemption, the interest rate on such series of Notes will increase by 2.50% beginning on (and including) the first day of the interest period following the interest period in which the Transaction Termination Event occurred until the maturity date of that series of Notes. See “Description of Notes—Special Optional Redemption upon a Transaction Termination Event.”

Purchase of Notes upon a Change of Control Triggering Event If a Change of Control Triggering Event (as defined herein) occurs, the Company will make an offer to each holder of Notes to repurchase all of that holder’s Notes at a repurchase price in cash equal to 101% of the aggregate principal amount of Notes repurchased (such principal amount to be equal to $2,000 or an integral multiple of $1,000 in excess thereof), plus accrued and unpaid interest, if any, on the Notes repurchased to, but excluding, the date of repurchase. See “Description of Notes—Purchase of Notes Upon a Change of Control Triggering Event.”

Further Issuances The Company may, from time to time, without notice to or the consent of the holders of the Notes, issue additional Notes under the Indenture (as defined herein), in which case any additional Notes so issued will have the same form and terms (other than the date of issuance and the public offering price and, under certain circumstances, the date from which interest thereon will begin to accrue and the initial interest payment date), and such additional Notes will form a single series with the previously issued Notes, including for voting purposes; provided that unless such additional Notes are issued in a “qualified reopening” of or otherwise part of the same “issue” as the previously issued Notes, or are issued with less than a de minimis amount of OID, in each case, for U.S. federal income tax purposes, such additional Notes will be issued with a different CUSIP, ISIN, Common Code and/or other securities identifier than the identifier used for such previously issued Notes.

Use of Proceeds We estimate that the net proceeds from the sale of the Notes will be approximately $      after deducting the underwriting discount and offering expenses.

We expect to use the net proceeds of this offering to fund a portion of the cash consideration payable in connection with the Transaction and, to the extent that any proceeds remain thereafter, or if the Transaction is not completed, for general corporate purposes including other acquisitions. In addition to the net proceeds from this offering, we expect to use available cash, including any cash raised in

S-5

the Common Stock Offering, and available borrowings under our credit agreement, dated June 22, 2023, as amended (our “Revolving Credit Facility”) or other borrowings to complete the Transaction.

This offering is not conditioned on the closing of the Transaction and there can be no assurance that the Transaction will be completed. The Notes offered hereby will remain outstanding whether or not the Transaction is completed, other than in the event of a Special Optional Redemption. See “Description of Notes—Special Optional Redemption upon a Transaction Termination Event” and “Use of Proceeds” below for more information.

Risk Factors You should carefully consider the information set forth in the section of this prospectus supplement entitled “Risk Factors” as well as the other information included in or incorporated by reference into this prospectus supplement, including the risk factors described in our Annual Report on Form 10-K for the fiscal year ended December 31, 2023, before deciding whether to invest in the Notes.

No Prior Market The Notes are a new issue of securities with no established trading market. The underwriters have advised us that they intend to make a market in the Notes, but they are not obligated to do so and may discontinue market-making at any time without notice. Accordingly, we cannot assure you that a liquid market for the Notes will develop or be maintained.

Certain Covenants We will issue the Notes under an Indenture that will, among other things, limit our ability to incur certain secured indebtedness and to consolidate, merge or sell all or substantially all of our assets. These limitations will be subject to a number of important qualifications and exceptions. See “Description of Notes.”

Governing Law The Notes and the Indenture under which they will be issued will be governed by New York law.

Trustee The Bank of New York Mellon Trust Company, N.A.

No Listing We do not intend to apply for listing of the Notes on any securities exchange or to arrange for the Notes to be quoted on any quotation system.

Form and Denomination The Notes will be issued in fully registered form in denominations of $2,000 and in integral multiples of $1,000 in excess thereof.

S-6

UNAUDITED PRO FORMA CONDENSED COMBINED FINANCIAL INFORMATION

The unaudited pro forma condensed combined financial information set forth below has been prepared in accordance with Article 11 of Regulation S-X as amended and should be read in conjunction with the accompanying notes to the unaudited pro forma condensed combined financial statements.

The unaudited pro forma condensed combined financial information was derived from and should be read in conjunction with:

• Audited consolidated financial statements and accompanying notes of the Company as of and for the fiscal year ended December 31, 2023 (as contained in its Annual Report on Form 10-K filed with the SEC on February 9, 2024);

• Unaudited consolidated financial statements and accompanying notes of the Company as of September 30, 2024 and for the nine months ended September 30, 2024 and 2023 (as contained in its Quarterly Report on Form 10-Q for the quarterly period ended September 30, 2024 filed with the SEC on October 29, 2024);

• Audited consolidated financial statements and accompanying notes of the Acquired Entity as of and for the year ended December 31, 2023 and unaudited consolidated financial statements and accompanying notes of the Acquired Entity as of September 30, 2024 and for the nine months ended September 30, 2024.

The unaudited pro forma condensed combined financial information is based on the historical consolidated financial statements of the Company and the historical consolidated financial statements of the Acquired Entity, as adjusted to give effect to the Transaction, this offering and the concurrent Common Stock Offering (collectively, the “Transactions” and, when referring only to this offering and the concurrent Common Stock Offering, the “Acquisition Financing”). The unaudited pro forma condensed combined balance sheet as of September 30, 2024 gives effect to the Transactions as if they occurred or had become effective on September 30, 2024. The unaudited pro forma condensed combined statements of earnings for the nine months ended September 30, 2024 and the fiscal year ended December 31, 2023, give effect to the Transactions as if they occurred or had become effective on January 1, 2023. Further information about this basis of presentation is provided in Note 1 to this unaudited pro forma condensed combined financial information.

The following unaudited pro forma condensed combined financial information provides for pro forma adjustments giving effect to the Transactions.

The unaudited pro forma condensed combined financial information has been prepared by us using the acquisition method of accounting in accordance with U.S. generally accepted accounting principles (“GAAP”). Gallagher has been treated as the acquirer in the Transaction for accounting purposes. The pro forma adjustments are based upon available information and certain assumptions that the Company believes are reasonable. The unaudited pro forma condensed combined financial information is provided for illustrative and informational purposes only and does not purport to represent or be indicative of the consolidated results of operations or financial condition of the Company had the Transactions been completed as of the dates presented and should not be construed as representative of the future consolidated results of operations or financial condition of the combined entity.

Provisional estimates of fair value of the Acquired Entity’s assets acquired and liabilities assumed will be subsequently reviewed and finalized within the first year of operations subsequent to the acquisition date to determine the necessity for adjustments. Fair value adjustments, if any, are most common to the values established for amortizable intangible assets, including expiration lists, trade name, and assembled workforce, with the offset to goodwill, net of any income tax effect. Provisional estimates of fair value were used by us to disclose the acquisition of the Acquired Entity as of the acquisition date. We are using independent third-party valuation specialists to assist us in determining the fair value of assets acquired and liabilities assumed for the

S-7

Transaction. As of this filing, the specialists have not completed their analysis and thus these fair value estimates are provisional. These provisional fair value estimates will be subsequently reviewed and adjusted based on the results of this valuation.

As a result of the foregoing, the pro forma adjustments are preliminary and have been made solely for the purpose of providing unaudited pro forma condensed combined financial information. Differences between these preliminary estimates and the final acquisition accounting may arise, and these differences could have a material impact on the accompanying unaudited pro forma condensed combined financial information and the combined Company’s future results of operations and financial position. See “Risk Factors—The unaudited pro forma condensed combined financial information reflecting the Transaction included in this prospectus supplement is based on assumptions and is subject to change based on various factors” for further information.

The unaudited pro forma condensed combined financial information does not reflect any expected cost savings, operating synergies or revenue enhancements that the combined entity may achieve as a result of the acquisition or the costs necessary to achieve any such cost savings, operating synergies or revenue enhancements.

S-8

UNAUDITED PRO FORMA CONDENSED COMBINED BALANCE SHEET

As of September 30, 2024

(in millions)

	Arthur J. Gallagher & Co. As Reported			Acquired Entity As Adjusted (Note 2)			Acquisition Financing Adjustments		Note 3	Transaction Accounting Adjustments			Note 4	Pro Forma Combined
Cash and cash equivalents	$	2,022.4		$	376.9		$	13,215.4	(a) (b)	$	(13,450.0	)	(b)	$	2,164.7
Fiduciary assets		30,836.3			703.9			—			—				31,540.2
Accounts receivable, net		3,988.8			654.5			—			—				4,643.3
Other current assets		435.2			142.9			—			—				578.1
Total current assets		37,282.7			1,878.2			13,215.4			(13,450.0	)			38,926.3
Fixed assets—net		660.1			167.0			—			—				827.1
Deferred income taxes		1,016.8			—			—			(1,016.8	)	(i)		—
Other noncurrent assets		1,361.8			130.1			—			(71.6	)	(c)		1,420.3
Right-of-use assets		374.7			155.4			—			—				530.1
Goodwill		12,193.4			5,848.4			—			2,474.0		(a) (b) (c) (d)		20,515.8
Amortizable intangible assets—net		4,353.2			3,042.4			—			2,681.7		(d)		10,077.3
Total assets	$	57,242.7		$	11,221.5		$	13,215.4		$	(9,382.7	)		$	72,296.9
Fiduciary liabilities	$	30,836.3		$	703.9		$	—		$	—			$	31,540.2
Accrued compensation and other current liabilities		3,222.5			703.0			—			10.0		(f)		3,935.5
Deferred revenue—current		680.8			69.8			—			—				750.6
Premium financing debt		259.9			—			—			—				259.9
Corporate related borrowings—current		200.0			33.3			—			(33.3	)	(a)		200.0
Total current liabilities		35,199.5			1,510.0			—			(23.3	)			36,686.2
Corporate related borrowings—noncurrent		7,791.9			6,484.7			4,907.2	(b)		(6,484.7	)	(a)		12,699.1
Deferred revenue—noncurrent		65.3			43.1			—			—				108.4
Lease liabilities—noncurrent		326.2			130.6			—			—				456.8
Deferred tax liabilities— noncurrent		96.0			396.1			—			(319.6	)	(i)		172.5
Other noncurrent liabilities		1,554.2			111.9			—			—				1,666.1
Total liabilities		45,033.1			8,676.4			4,907.2			(6,827.6	)			51,789.1
Mezzanine equity
Redeemable Series A Preferred Stock		—			297.5			—			(297.5	)	(a)		—
Stockholders’ equity
Common stock		219.4			—			31.0	(a)		—				250.4
Capital in excess of par value		7,697.4			2,384.3			8,277.2	(a)		(2,384.3	)	(a)		15,974.6
Retained earnings		4,860.6			(130.3	)		—			120.3		(a) (f)		4,850.6
Accumulated other comprehensive loss		(593.4	)		(6.4	)		—			6.4		(a)		(593.4	)
Stockholders’ equity attributable to controlling interests		12,184.0			2,545.1			8,308.2			(2,555.1	)			20,482.2
Stockholders’ equity attributable to noncontrolling interests		25.6			—			—			—				25.6
Total stockholders’ equity		12,209.6			2,545.1			8,308.2			(2,555.1	)			20,507.8
Total liabilities, mezzanine equity, and stockholders’ equity	$	57,242.7		$	11,221.5		$	13,215.4		$	(9,832.7	)		$	72,296.9

See accompanying notes to unaudited pro forma condensed combined financial information

S-9

UNAUDITED PRO FORMA CONDENSED COMBINED STATEMENT OF EARNINGS

For the Nine Months Ended September 30, 2024

(in millions, except per share data)

	Arthur J. Gallagher & Co. As Reported			Acquired Entity As Adjusted (Note 2)			Acquisition Financing Adjustments			Note 3		Transaction Accounting Adjustments			Note 4		Pro Forma Combined
Commissions	$	5,193.2		$	1,704.2		$	—				$	—				$	6,897.4
Fees		2,723.3			330.3			—					—					3,053.6
Supplemental revenues		261.7			—			—					—					261.7
Contingent revenues		215.1			182.4			—					—					397.5
Interest income, premium finance revenues and other income		327.3			18.5			—					—					345.8
Revenues before reimbursements		8,720.6			2,235.4			—					—					10,956.0
Reimbursements		118.3			—			—					—					118.3
Total revenues		8,838.9			2,235.4			—					—					11,074.3
Compensation		4,967.9			1,189.4			—					10.1			(c)		6,167.4
Operating		1,315.0			349.8			—					—					1,664.8
Reimbursements		118.3			—			—					—					118.3
Interest		279.4			439.5			204.8			(c)		(439.5	)		(h)		484.2
Depreciation		131.5			28.4			—					—					159.9
Amortization		497.8			248.2			—					36.8			(e) (h)		782.8
Loss on extinguishment of debt		—			3.4			—					—					3.4
Change in estimated acquisition earnout payables		(12.6	)		68.6			—					—					56.0
Total expenses		7,297.3			2,327.3			204.8					(392.6	)				9,436.8
Earnings before income taxes		1,541.6			(91.9	)		(204.8	)				392.6					1,637.5
Provision (benefit) for income taxes		329.4			(17.4	)		(53.2	)		(d)		102.1			(g)		360.9
Net earnings (loss)		1,212.2			(74.5	)		(151.6	)				290.5					1,276.6
Net earnings attributable to noncontrolling interests		7.8			—			—					—					7.8
Net earnings attributable to controlling interests	$	1,204.4		$	(74.5	)	$	(151.6	)			$	290.5				$	1,268.8
Basic net earnings per share (5)	$	5.51															$	5.09
Diluted net earnings per share (5)	$	5.40															$	5.00

See accompanying notes to unaudited pro forma condensed combined financial information

S-10

UNAUDITED PRO FORMA CONDENSED COMBINED STATEMENT OF EARNINGS

For the Twelve Months Ended December 31, 2023

(in millions, except per share data)

	Arthur J. Gallagher & Co. As Reported			Acquired Entity As Adjusted (Note 2)			Acquisition Financing Adjustments			Note 3		Transaction Accounting Adjustments			Note 4		Pro Forma Combined
Commissions	$	5,865.0		$	1,962.2		$	—				$	—				$	7,827.2
Fees		3,144.7			392.6			—					—					3,537.3
Supplemental revenues		314.2			—			—					—					314.2
Contingent revenues		235.3			198.9			—					—					434.2
Interest income, premium finance revenues and other income		367.3			34.5			—					—					401.8
Revenues before reimbursements		9,926.5			2,588.2			—					—					12,514.7
Reimbursements		145.4			—			—					—					145.4
Total revenues		10,071.9			2,588.2			—					—					12,660.1
Compensation		5,681.2			1,389.3			—					11.8			(c)		7,082.3
Operating		1,689.7			407.8			—					10.0			(f)		2,107.5
Reimbursements		145.4			—			—					—					145.4
Interest		296.7			492.9			273.0			(c)		(492.9	)		(h)		569.7
Depreciation		165.2			28.2			—					—					193.4
Amortization		531.3			248.0			—					156.0			(e) (h)		935.3
Loss on extinguishment of debt		—			3.2			—					—					3.2
Change in estimated acquisition earnout payables		377.3			85.9			—					—					463.2
Total expenses		8,886.8			2,655.3			273.0					(315.1	)				11,500.0
Earnings before income taxes		1,185.1			(67.1	)		(273.0	)				315.1					1,160.1
Provision (benefit) for income taxes		219.1			(11.4	)		(71.0	)		(d)		81.9			(g)		218.6
Net earnings (loss)		966.0			(55.7	)		(202.0	)				233.2					941.5
Net earnings (loss) attributable to noncontrolling interests		(3.5	)		—			—					—					(3.5	)
Net earnings attributable to controlling interests	$	969.5		$	(55.7	)	$	(202.0	)			$	233.2				$	945.0
Basic net earnings per share (5)	$	4.51															$	3.84
Diluted net earnings per share (5)	$	4.42															$	3.78

See accompanying notes to unaudited pro forma condensed combined financial information

S-11

NOTES TO UNAUDITED PRO FORMA CONDENSED COMBINED FINANCIAL STATEMENTS

Note 1—Basis of presentation

The unaudited pro forma condensed combined financial information has been prepared by Gallagher in connection with the Company’s acquisition of the Acquired Entity.

The unaudited condensed combined pro forma financial information and related notes were prepared in accordance with Article 11 of Regulation S-X and are based on the historical consolidated financial statements of the Company and the historical consolidated financial statements of the Acquired Entity, as adjusted to give effect to the pro forma adjustments described below.

The pro forma adjustments to the statements of earnings have been prepared as if the Transactions occurred on January 1, 2023. The pro forma adjustments to the balance sheet have been prepared as if the Transactions occurred on September 30, 2024. The historical consolidated financial information has been adjusted in the unaudited pro forma condensed combined financial statements in accordance with Article 11 of Regulation S-X as amended. The pro forma adjustments are based on currently available information and certain estimates and assumptions, and therefore the actual effect of these transactions may differ from the pro forma adjustments.

Gallagher and the Acquired Entity’s historical financial statements were prepared in accordance with U.S. GAAP.

The audited consolidated financial statements and accompanying notes of the Acquired Entity as of and for the year ended December 31, 2023 and the unaudited condensed consolidated financial statements and accompanying notes of the Acquired Entity as of September 30, 2024 and for the nine months ended September 30, 2024 are attached as Exhibits 99.2 and 99.3 to Gallagher’s Current Report on Form 8-K filed with the SEC on December 9, 2024.

The accompanying unaudited pro forma condensed combined financial information and related notes were prepared using the acquisition method of accounting in accordance with Accounting Standards Codification (“ASC”) Topic 805, Business Combinations (“ASC 805”), with Gallagher considered the accounting acquirer of the Acquired Entity. ASC 805 requires, among other things, that the assets acquired, and liabilities assumed in a business combination be recognized at their fair values as of the acquisition date. For purposes of the unaudited pro forma condensed combined balance sheet, the purchase price consideration has been allocated to the assets acquired and liabilities assumed of the Acquired Entity based upon management’s preliminary estimate of their fair values as of September 30, 2024. The excess of the purchase price consideration over the fair value of assets acquired and liabilities assumed is allocated to goodwill. Accordingly, the purchase price allocation and related adjustments reflected in the unaudited pro forma condensed combined financial information are preliminary and subject to adjustment based on a final determination of fair value. The purchase price consideration as well as the estimated fair values of the assets and liabilities will be updated and finalized as soon as practicable, but no later than one year from the closing of the acquisition.

The pro forma adjustments are based upon available information and certain assumptions that Gallagher believes are reasonable. Management has included certain reclassification and policy alignment adjustments for consistency in presentation as indicated in the subsequent notes (see Note 2 for further details). The unaudited pro forma condensed combined financial information is provided for informational purposes only and does not purport to represent or be indicative of the consolidated results of operations or financial condition of the Company had the Transactions been completed as of the dates presented and should not be construed as representative of the future consolidated results of operations or financial condition of the combined entity.

S-12

Note 2—Reclassification adjustments

Certain balances were reclassified from the Acquired Entity’s historical financial statements so its presentation would be consistent with that of Gallagher. These reclassifications are based on management’s preliminary analysis and have no effect on separately reported net assets, equity or net earnings attributed to common shareholders of the Acquired Entity.

When the Company completes its detailed review of the Acquired Entity’s chart of accounts and accounting policies, additional reclassification adjustments could be identified that, when conformed, could have a material impact on the combined Company’s financial information. Refer to the table below for a summary of the reclassification adjustments made to the Acquired Entity’s unaudited condensed consolidated balance sheet as of September 30, 2024 to conform its presentation to that of Gallagher.

Arthur J. Gallagher & Co. Presentation	Acquired Entity Presentation	Historical Acquired Entity at September 30, 2024		Reclassification Adjustments			Note	Historical Acquired Entity as adjusted For Arthur J. Gallagher & Co.
Cash and cash equivalents	Cash and cash equivalents		342.2		34.7		(a)		376.9
	Restricted cash		60.0		(60.0	)	(a)
	Trust cash		292.2		(292.2	)	(a)
	Fixed maturity securities		37.8		(37.8	)	(b)
Fiduciary assets			—		703.9		(a)		703.9
Accounts receivable, net	Accounts receivable, net		1,040.9		(386.4	)	(a)		654.5
	Prepaid expenses		36.7		(36.7	)	(b)
Other current assets	Other current assets		68.4		74.5		(b)		142.9
	Accounts receivable, noncurrent portion		37.2		(37.2	)	(c)
Fixed assets—net	Fixed assets – net		167.0		—				167.0
Deferred income taxes			—		—
Other noncurrent assets	Other noncurrent assets		92.9		37.2		(c)		130.1
Right-of-use assets	Operating lease right-of-use assets, net		155.4		—				155.4
Goodwill	Goodwill		5,848.4		—				5,848.4
Amortizable intangible assets—net	Definite-lived intangible assets, net		3,042.4		—				3,042.4
Total assets			11,221.5		—				11,221.5
Fiduciary liabilities			—		703.9		(a)		703.9
	Long-term debt, net, current portion		33.3		(33.3	)	(d)
	Earn-out payables, current portion		279.9		(279.9	)	(e)
	Carrier payables		567.4		(567.4	)	(a)
	Accounts payable		90.4		(79.3 (11.1	)  )	(a) (f)
	Customer advances		57.2		(57.2	)	(a)
	Producer payables		137.2		(137.2	)	(f)
	Reserve for unpaid losses and loss adjustment expenses, current portion		5.6		(5.6	)	(f)
	Accrued expenses and other		269.2		(269.2	)	(f)
Accrued compensation and other current liabilities			—		703.0		(f) (e)		703.0
Deferred revenue—current	Deferred revenue – current		69.8		—				69.8
Corporate related borrowings—current			—		33.3		(d)		33.3
Corporate related borrowings—noncurrent			—		6,484.7		(h)		6,484.7
Deferred revenue—noncurrent	Deferred revenue – noncurrent		43.1		—				43.1
	Earn-out payables, noncurrent portion		66.1		(66.1	)	(g)
	Long-term debt, net, noncurrent portion		6,484.7		(6,484.7	)	(h)

S-13

Arthur J. Gallagher & Co. Presentation	Acquired Entity Presentation	Historical Acquired Entity at September 30, 2024			Reclassification Adjustments			Note		Historical Acquired Entity as adjusted For Arthur J. Gallagher & Co.
	Reserve for unpaid losses and loss adjustment expenses, noncurrent portion		22.5			(22.5	)		(g)
	Operating lease liabilities, noncurrent portion		130.6			(130.6	)		(i)
Lease liabilities—noncurrent			—			130.6			(i)		130.6
Deferred income taxes—noncurrent	Deferred income taxes, net		396.1			—					396.1
Other noncurrent liabilities	Other noncurrent liabilities		23.3			88.6			(g)		111.9
Total liabilities			8,676.4			—					8,676.4
	Redeemable Series A Preferred Stock		297.5			—					297.5
Total Mezzanine equity			297.5			—					297.5
Common stock			—			—
Capital in excess of par value			2,384.3			—					2,384.3
Accumulated other comprehensive loss	Accumulated other comprehensive (loss) income		(6.4	)		—					(6.4	)
Retained earnings	Retained earnings		(130.3	)		—					(130.3	)
Total liabilities and stockholder’s equity			11,221.5			—					11,221.5

(a) Represents the reclassification of the Acquired Entity’s “Restricted cash” amount to “Cash and cash equivalents” and the reclassification of “Trust Cash” and “Agency bill accounts receivables” amounts to “Fiduciary assets” to conform to Gallagher’s historical presentation. Additionally, represents the reclassification of the Acquired Entity’s “Carrier payables,” “Customer advances” and select “Accounts payable” amounts to “Fiduciary liabilities” to conform to Gallagher’s historical presentation.

(b) Represents the combination and reclassification of the Acquired Entity’s “Fixed maturity securities” and “Prepaid expenses” amounts to “Other current assets” to conform to Gallagher’s historical presentation.

(c) Represents the reclassification of the Acquired Entity’s “Accounts receivable, noncurrent portion” amounts to “Other noncurrent assets” to conform to Gallagher’s historical presentation.

(d) Represents the combination and reclassification of the Acquired Entity’s “Long-term debt, net, current portion” amounts to “Corporate related borrowings – current” to conform to Gallagher’s historical presentation.

(e) Represents the combination and reclassification of the Acquired Entity’s “Earn-out payables, current portion” amounts to “Accrued compensation and other current liabilities” to conform to Gallagher’s historical presentation.

(f) Represents the combination and reclassification of the Acquired Entity’s “Accounts payable,” “Producer payables,” “Reserve for unpaid losses and loss adjustment expenses, current portion” and “Accrued expenses and other” amounts to “Accrued compensation and other current liabilities” to conform to Gallagher’s historical presentation.

(g) Represents the combination and reclassification of the Acquired Entity’s “Earn-outs payables, noncurrent portion” and “Reserve for unpaid losses and loss adjustment expenses, noncurrent portion” amounts to “Other noncurrent liabilities” to conform to Gallagher’s historical presentation.

(h) Represents the combination and reclassification of the Acquired Entity’s “Long-term debt, net, noncurrent portion” amounts to “Corporate related borrowings—noncurrent” to conform to Gallagher’s historical presentation.

(i) Represents the combination and classification of the Acquired Entity’s “Operating lease liabilities, noncurrent portion” amounts to “Lease liabilities—noncurrent” to conform to Gallagher’s historical presentation.

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Refer to the tables below for a summary of the reclassification adjustments made to the Acquired Entity’s unaudited condensed consolidated statements of comprehensive income for the nine months ended September 30, 2024 and the year ended December 31, 2023 to conform its presentation to that of Gallagher.

Arthur J. Gallagher & Co. Presentation	Acquired Entity Presentation	Historical Acquired Entity for the period ended September 30, 2024			Reclassification Adjustments			Note			Historical Acquired Entity Adjusted for Arthur J. Gallagher & Co.
Commissions			—			1,704.2			(a	)		1,704.2
Fees			—			330.3			(a	)		330.3
	Commissions and fees		2,034.5			(2,034.5	)		(a	)		—
Supplemental revenues			—			—						—
Contingent revenues	Contingent revenues		182.4			—						182.4
	Investment income		5.0			(5.0	)		(b	)		—
Interest income, premium finance revenues and other income			—			18.5			(b	) (e)		18.5
	Interest income		14.1			(14.1	)		(b	)		—
Reimbursements			—			—						—
Total revenues			2,236.0			(0.6	)					2,235.4
Compensation	Compensation expense		1,189.4			—						1,189.4
	Selling expense		43.7			(43.7	)		(c	)		—
	Administrative expense		300.9			(300.9	)		(c	)		—
	Transaction expense		5.2			(5.2	)		(c	)		—
Operating			—			349.8			(c	)		349.8
Reimbursements			—			—						—
Interest	Interest		439.5			—						439.5
	Depreciation and amortization expense		276.6			(276.6	)		(d	)		—
Depreciation			—			28.4			(d	)		28.4
Amortization			—			248.2			(d	)		248.2
	Other (Income) expense, net		0.6			(0.6	)		(e	)		—
Debt extinguishment loss	Debt extinguishment loss		3.4			—						3.4
	Change in estimated acquisition earnout payables		68.6			—						68.6
Total expenses			2,327.9			(0.6	)					2,327.3
Earnings before income taxes			(91.9	)		—						(91.9	)
Provision (benefit) for income taxes	Provision (benefit) for income taxes		(17.4	)		—						(17.4	)
Net earnings			(74.5	)		—						(74.5	)

(a) Represents the reclassification of the Acquired Entity’s “Commission and fees” amounts to “Commissions” and “Fees” to conform to Gallagher’s historical presentation.

(b) Represents the combination and reclassification of the Acquired Entity’s “Investment income” and “Interest income” amounts to “Interest income, premium finance revenues and other income” to conform to Gallagher’s historical presentation.

(c) Represents the combination and reclassification of the Acquired Entity’s “Selling expense,” “Administrative expense” and “Transaction expense” amounts to “Operating” to conform to Gallagher’s historical presentation.

(d) Represents the reclassification of the Acquired Entity’s “Depreciation and amortization” amounts to “Depreciation” and “Amortization” to conform to Gallagher’s historical presentation.

(e) Represents the reclassification of the Acquired Entity’s “Other (Income) expense, net” amounts to “Interest income, premium finance revenues and other income” to conform to Gallagher’s historical presentation.

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Arthur J. Gallagher & Co. Presentation	Acquired Entity Presentation	Historical Acquired Entity for the period ended December 31, 2023			Reclassification Adjustments			Note	Historical Acquired Entity adjusted for Arthur J. Gallagher & Co.
Commissions			—			1,962.2		(a)		1,962.2
Fees			—			392.6		(a)		392.6
	Commissions and fees		2,354.8			(2,354.8	)	(a)		—
Supplemental revenues			—			—				—
Contingent revenues	Contingent revenues		198.9			—				198.9
	Investment income		1.8			(1.8	)	(b)		—
Interest income, premium finance revenues and other income			—			34.5		(b) (e)		34.5
	Interest income		27.8			(27.8	)	(b)		—
Reimbursements			—			—				—
Total revenues			2,583.3			4.9				2,588.2
Compensation	Compensation expense		1,389.3			—				1,389.3
	Selling expense		48.1			(48.1	)	(c)		—
	Administrative expense		344.1			(344.1	)	(c)		—
	Transaction expense		15.6			(15.6	)	(c)		—
Operating			—			407.8		(c)		407.8
Interest	Interest		492.9			—				492.9
	Depreciation and amortization expense		276.2			(276.2	)	(d)		—
Depreciation			—			28.2		(d)		28.2
Amortization			—			248.0		(d)		248.0
	Other (Income) expense, net		(4.9	)		4.9		(e)		—
Debt extinguishment loss	Debt extinguishment loss		3.2			—				3.2
	Change in estimated acquisition earnout payables		85.9			—				85.9
Total expenses			2,650.4			4.9				2,655.3
Earnings before income taxes			(67.1	)		—				(67.1	)
Provision (benefit) for income taxes	Provision (benefit) for income taxes		(11.4	)		—				(11.4	)
Net earnings			(55.7	)		—				(55.7	)

(a) Represents the reclassification of the Acquired Entity’s “Commission and fees” amounts to “Commissions” and “Fees” to conform to Gallagher’s historical presentation.

(b) Represents the reclassification of the Acquired Entity’s “Investment income” and “Interest income” amounts to “Interest income, premium finance revenues and other income” to conform to Gallagher’s historical presentation.

(c) Represents the combination and reclassification of the Acquired Entity’s “Selling expense,” “Administrative expense” and “Transaction expense” amounts to “Operating” to conform to Gallagher’s historical presentation.

(d) Represents the reclassification of the Acquired Entity’s “Depreciation and amortization” amounts to “Depreciation” and “Amortization” to conform to Gallagher’s historical presentation.

(e) Represents the reclassification of the Acquired Entity’s “Other (Income) expense, net” amounts to “Interest income, premium finance revenues and other income” to conform to Gallagher’s historical presentation.

Note 3—Financing adjustments

Prior to the close of the Transaction, Gallagher signed the Purchase Agreement on December 7, 2024 to acquire the Acquired Entity. To finance the planned acquisition, Gallagher expects to:

(a) close on a follow-on offering of its common stock, whereby 31 million shares of common stock are expected to be issued for net proceeds of $8,308.2 million, after underwriting discounts and other expenses related to the offering.

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(b) close and fund a debt offering of $4,950 million aggregate principal amount with a weighted average interest rate of 5.40% (the “Notes”).

Based on Gallagher’s financing for the Transaction, the impacts to the condensed combined pro forma balance sheet were as follows:

(a) Reflects the cash proceeds of $8,308.2 million, net of issuance costs and underwriting discounts related to the follow-on offering of common stock.

(b) Reflects the cash proceeds, net of issuance costs and underwriting discounts, related to issuance of the Notes. These Notes were issued at a principal amount of $4,950 million with issuance costs and underwriting discounts of $42.8 million amortized over the life of the notes.

The impacts to the condensed combined pro forma statements of earnings were as follows:

(c) Reflects the pro forma interest expense and amortized issuance costs and discounts adjustment for the nine months ended September 30, 2024 and year ended December 31, 2023, calculated as follows:

(in millions)	Amount
Notes principal	$	4,950
Annual weighted average interest rate		5.40	%
Annual interest on Notes	$	270
Total Notes issuance cost and underwriting discount	$	42.8
Notes term (years)		12.5
Annual amortized debt issuance cost and discount	$	3.0
Amortized debt issuance cost and discount for 9 months ended September 30, 2024	$	2.3
Pro forma interest and amortization expense for 9 months ended September 30, 2024	$	204.8
Pro forma interest and amortization expense for year-ended December 31, 2023	$	273.0

(d) Reflects the U.S. income tax benefit of the interest expense related to the Acquisition Financing using an estimated blended U.S. federal and state income tax rate of 26%. Because the adjustments contained in the unaudited pro forma condensed combined financial information are based on estimates, the effective tax rate herein will likely vary from the effective rate in periods subsequent to the Transaction.

Note 4—Transaction accounting adjustments

Under the terms of the Purchase Agreement, the Company expects to acquire the Acquired Entity for total consideration of $13,450 million. The debt and equity transactions to raise the cash necessary to finance the planned acquisition are discussed in Note 3. The Company is not expected to assume any outstanding borrowings of the Acquired Entity. The following table summarizes the source of the estimated purchase consideration.

(in millions)	Amount
Total purchase consideration	$	13,450.0

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The following is a summary of the estimated fair values of the identifiable tangible and intangible assets acquired and liabilities assumed as if the Transaction occurred on September 30, 2024 (in millions):

(in millions)	Amount
Cash and cash equivalents	$	376.9
Fiduciary assets		703.9
Accounts receivable, net of allowance for credit losses		654.5
Other current assets		142.9
Fixed assets, net		167.0
Goodwill		8,322.4
Definite-lived intangible assets, net		5,724.1
Operating lease right-of-use assets, net		155.4
Other noncurrent assets, net		58.5
Total assets	$	16,305.6
Fiduciary liabilities	$	703.9
Accrued compensation and other current liabilities		703.0
Deferred revenue, current		69.8
Deferred revenue, noncurrent		43.1
Lease liabilities, noncurrent		130.6
Deferred income taxes, noncurrent		1,093.3
Other noncurrent liabilities		111.9
Total liabilities	$	2,855.6

The preliminary estimates are based on the data available to Gallagher and may change upon completion of the final purchase price allocation. Any change in the estimated fair value of the assets and liabilities acquired may have a corresponding impact on the amount of the goodwill. In addition, only intangible assets were evaluated for fair value. The goodwill amount represents the total purchase consideration less the preliminary fair value of net assets acquired. Goodwill will not be amortized but instead will be tested for impairment at least annually (or more frequently if indicators of impairment arise). When the Company completes its detailed review of the Acquired Entity’s accounting policies, additional reclassifications could be identified that, when confronted, could have a material impact on the combined Company’s financial information.

The impacts to the condensed combined pro forma balance sheet from the Transaction were as follows:

(in millions)	Amount
Cash consideration (b)	$	13,450.0
Elimination of deferred commissions (c)		71.6
Deferred tax adjustment (i)		697.2
Fair value step up of intangibles (d)		(2,681.7	)
Elimination of historical Acquired Entity debt (a)		(6,518.0	)
Elimination of historical Acquired Entity equity (a)		(2,545.1	)
Total adjustment to goodwill		2,474.0
Historical Acquired Entity goodwill		5,848.4
Total goodwill from Transaction	$	8,322.4

(a) Reflects adjustment to write off the equity (including retained earnings) of the Acquired Entity and reflects the repayment of the Acquired Entity’s outstanding corporate borrowings, which is expected to occur as part of the transaction.

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(b) Reflects the $13,450 million cash transferred in connection with the close of the Transaction.

(c) Reflects the reversal of deferred commissions in the Acquired Entity’s Balance Sheet and recording of expenses as incurred to the pro forma combined statement of earnings, consistent with Company’s accounting policy for costs to obtain contracts with customers.

(d) Reflects the impact of fair value step up of acquired trade names and expiration lists, as compared to the carrying value for the Acquired Entity as of September 30, 2024. The estimated fair value of acquired trade names is $24.0 million, and the estimated value of expiration lists is $5,700 million.

The impacts to the condensed combined pro forma statements of earnings from the Transaction were as follows:

(e) Reflects an adjustment to Amortization for the intangible expiration lists amortization expense based on the fair values and estimated useful life below. There was no previous expiration lists amortization expense in the Acquired Entity’s historical financial results to remove.

(in millions)	Amount
Expiration lists fair value	$	5,700.0
Estimated useful life		15 years
Annual straight line amortization expense	$	380.0
9 months straight line amortization expense	$	285.0

Reflects an adjustment to Amortization for the intangible trade names amortization expense based on the fair values and estimated useful life below. The historical amortization related to trade names has been adjusted as noted in tickmark (h).

(in millions)	Amount
Trade names fair value	$	24.0
Estimated useful life		1 year
Annual straight line amortization expense	$	24.0
9 months straight line amortization expense		—

(f) Reflects the estimated one-time transaction-related costs incurred which have not been reflected in the Company’s historical statements of earnings for the year ended December 31, 2023 or nine months ended September 30, 2024, or balance sheet as of September 30, 2024.

(g) Reflects the U.S. income tax expense of the Transaction pro forma adjustments using an estimated blended U.S. federal and state income tax rate of 26%. Because the adjustments contained in the unaudited pro forma condensed combined financial information are based on estimates, the effective tax rate herein will likely vary from the effective rate in periods subsequent to the Transaction.

(h) Reflects the adjustment for the reversal of historical amortization and interest booked related to the Acquired Entity’s debt, which is written off in (a) above and is not expected to legally convey as part of the Transaction.

(i) Reflects the deferred tax balance sheet adjustment for the impact of purchase price adjustments for the fair value of intangible assets. Additionally, reflects the reclassification of the Company’s deferred tax asset related to US book-tax differences to Deferred tax liabilities—noncurrent, to present the net deferred tax liability within Deferred tax liabilities—noncurrent:

(in millions)	Amount
Deferred tax liability for fair value intangible adjustment	$	697.2
Company DTA reclassified to Deferred tax liabilities – noncurrent		(1,016.8	)
Net deferred tax adjustment to Deferred tax liabilities – noncurrent	$	(319.6	)

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Note 5—Net earnings per share

Basic net earnings per share is computed by dividing net earnings by the weighted average number of common shares outstanding during the reporting period. Diluted net earnings per share is computed by dividing net earnings by the weighted average number of common and common equivalent shares outstanding during the reporting period. Common equivalent shares include incremental shares from dilutive stock options, which are calculated from the date of grant under the treasury stock method using the average market price for the period.

The following table sets forth the computation of pro forma basic and diluted net earnings per share (in millions, except per share data):

(in millions)	Nine months Ended September 30, 2024			Year ended December 31, 2023
Net earnings attributable to controlling interests of Gallagher	$	1,204.4		$	969.5
Net earnings attributable to controlling interests of Acquired Entity		(74.5	)		(55.7	)
Pro Forma adjustments to net earnings attributable to controlling interest		138.9			31.2
Pro Forma net earnings attributable to controlling interest		1,268.8			945.0
Weighted average number of common shares outstanding		218.5			214.9
Follow-on public offering		31.0			31.0
Pro Forma weighted average number of common shares outstanding		249.5			245.9
Dilutive effect of stock options using the treasury stock method		4.4			4.4
Pro Forma weighted average number of common and common equivalent shares outstanding		253.9			250.3
Pro Forma basic net earnings per share	$	5.09		$	3.84
Pro Forma diluted net earnings per share	$	5.00		$	3.78

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RISK FACTORS

Investing in the Notes involves risks, including the risks described below that are specific to the Notes and those that could affect us and our business. You should not purchase the Notes unless you understand these investment risks. Please be aware that other risks may prove to be important in the future. New risks may emerge at any time and we cannot predict such risks or estimate the extent to which they may affect our financial performance. Before purchasing any Notes, you should consider carefully the risks and other information in this prospectus supplement and the accompanying prospectus and the documents incorporated by reference herein and therein, including the section entitled “Risk Factors” in our Annual Report on Form 10-K for the fiscal year ended December 31, 2023.

Risks Relating to the Proposed Transaction

We may encounter integration challenges and the Transaction may not perform as expected.

We can provide no assurance that we will be able to successfully integrate the operations acquired in the Transaction or achieve expected cost savings or synergies from such integration, that the acquired operations will perform as expected or that we will not incur unforeseen obligations or liabilities. It is possible that our experience in running the operations acquired in the Transaction will require us to adjust our expectations regarding the impact of the acquisition on our operating results. In addition, integration efforts are anticipated to be complex and may divert management attention and resources, which could adversely affect our operating results.

There can be no assurance that we will be able to secure the required financing in connection with the acquisition on acceptable terms, at favorable pricing, in a timely manner or at all.

We expect to finance the Transaction using the net proceeds of this offering, available cash and available borrowings under our Revolving Credit Facility, other borrowings and/or, subject to market conditions and other factors, the Common Stock Offering. The completion of the Transaction is not conditioned on our ability to obtain financing. If our ability to raise funds through the capital markets is impacted for any reason, including, but not limited to, a deterioration in our financial results, poor economic conditions, or stock market volatility, we may be unable to complete equity and/or debt offerings on acceptable terms, at favorable pricing, in a timely manner, or at all. Additionally, the cost of financing the Transaction could be more expensive than expected. If we are unable to obtain such financing as anticipated, we may be compelled to specifically perform our obligations to complete the Transaction or could otherwise be subject to claims under the Purchase Agreement, each of which could have a material adverse effect on the Company.

The unaudited pro forma condensed combined financial information reflecting the Transaction included in this prospectus supplement is based on assumptions and is subject to change based on various factors.

We and the Acquired Entity have no prior history as a combined company and our assets and operations have not been managed on a combined basis. As a result, our unaudited pro forma condensed combined financial information included in this prospectus supplement, which was prepared in accordance with Article 11 of Regulation S-X, and historical financial statements of our and the Acquired Entity’s businesses are presented for informational purposes only and are not necessarily indicative of the financial position or results of operations that would have actually occurred had the Transaction and related financings been completed at or as of the dates indicated, nor is it indicative of the future operating results or financial position of the combined company if the Transaction and related financings are consummated.

Our unaudited pro forma condensed combined financial information does not reflect any cost savings, operating synergies, or revenue enhancements that the combined company may achieve as a result of the Transaction, nor does it reflect the costs to integrate the operations of the Company or the costs necessary to

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achieve any cost savings, operating synergies, and revenue enhancements. Our unaudited pro forma condensed combined financial information included in this prospectus supplement is based in part on certain assumptions regarding the Transaction and the related financings. We believe the assumptions underlying such unaudited pro forma condensed combined financial information are reasonable under the circumstances, however, such assumptions and estimates are preliminary and may not prove to be accurate over time. In addition, if and to the extent there are any changes in market conditions affecting the financings, then the pro forma condensed combined financial information and the future operating results or financial position of the combined company may be impacted, and such impact may be material. We have no obligation to update the pro forma condensed financial information incorporated by reference herein for any subsequent event and may not do so.

As a result, investors should not place any undue reliance on our unaudited pro forma financial information, and our actual results following the completion of the Transaction and related financings may differ from those that are anticipated.

Certain financial information related to the Acquired Entity presented in this prospectus supplement is derived from financial statements that are not included herein and include certain non-GAAP measures and investors are cautioned not to place undue reliance on such information.

AssuredPartners is the operating subsidiary of the Acquired Entity. The Acquired Entity’s financial information for the twelve months ended September 30, 2024 presented in this prospectus supplement is partially derived from AssuredPartners’ standalone financial statements that are not included or incorporated by reference in this prospectus supplement. The AssuredPartners standalone financial statements are substantially similar to the consolidated financial statements of the Acquired Entity incorporated by reference into this prospectus supplement except for certain differences as a result of ordinary course differences of presentation of certain line items and transactions involving the Acquired Entity. In addition, the Company’s management applied certain adjustments to the Acquired Entity’s financial information to calculate the Acquired Entity’s pro forma Adjusted EBITDAC, including non-recurring legal, transaction-related, technology and acquisition-related compensation expense. These adjustments are substantially similar to the adjustments management makes when calculating the Company’s non-GAAP measures included in this prospectus supplement and assisted management in its assessment of the acquisition of the Acquired Entity. These non-GAAP measures should not be considered substitutes for any performance metric determined in accordance with GAAP. Investors are cautioned not to place undue reliance on the AssuredPartners’ financial information or the Acquired Entity’s non-GAAP measures.

We have made certain assumptions relating to the Transaction which may prove to be materially inaccurate.

We have made certain assumptions relating to the Transaction, which assumptions involve significant judgement and may not reflect the full range of uncertainties and unpredictable outcomes inherent in the Transaction and may be materially inaccurate. These assumptions relate to numerous matters, including:

• our ability to realize the expected benefits of the Transaction;

• projections of future revenue, EBITDAC and our earnings per share;

• our ability to maintain, develop and deepen relationships with employees, including key brokers, and customers associated with the Acquired Entity;

• our ability to issue equity and debt or any other financing, or to generate and maintain needed cash from operations, to complete the Transaction and the impact of such financing on our operating results or financial condition;

• projections of future expenses and expense allocation relating to the Transaction and the Acquired Entity;

• unknown or contingent liabilities associated with the Transaction or the Acquired Entity;

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• the amount of goodwill and intangibles that will result from the Transaction;

• other purchase accounting adjustments that we may record in our financial statements in connection with the Transaction;

• acquisition and integration costs, including restructuring charges and transaction costs; and

• other financial and strategic risks of the Transaction.

In the event that the closing of the Transaction has not occurred on or prior to the earlier of (i) March 9, 2026 and (ii) the date the Purchase Agreement is terminated, we will have the option to redeem any or all series of Notes at a redemption price equal to 101% of the aggregate principal amount of the series of Notes being redeemed, together with accrued and unpaid interest thereon, if any, and, as a result, holders of the Notes may not obtain their expected return on the Notes.

We may not consummate the Transaction within the timeframe specified under “Description of Notes—Special Optional Redemption upon a Transaction Termination Event,” or the Transaction may be terminated. Our ability to consummate the Transaction is subject to customary closing conditions over which we have limited or no control, including regulatory approvals. In the event that the closing of the Transaction has not occurred on or prior to the earlier of (i) March 9, 2026 and (ii) the date the Purchase Agreement is terminated, we will have the option to redeem, in whole but not in part, any or all series of Notes at a redemption price equal to 101% of the aggregate principal amount of the series being redeemed, together with accrued and unpaid interest, if any, to, but excluding, the redemption date. If we redeem any Notes pursuant to the Special Optional Redemption, you may not obtain your expected return on those Notes. Your decision to invest in the Notes is made at the time of the offering of the Notes. You will have no rights under the Special Optional Redemption provision if the closing of the Transaction occurs within the specified timeframe, nor will you have any right to require us to redeem your Notes if the Transaction does not close.

Risks Relating to the Notes

We depend on cash flow of our subsidiaries to make payments on our securities.

Arthur J. Gallagher & Co. is a holding company. Our subsidiaries conduct substantially all of our consolidated operations and own a significant percentage of our consolidated assets. Consequently, our cash flow and our ability to meet our debt service obligations depend in large part upon the cash flow of our subsidiaries and the payment of funds by the subsidiaries to us in the form of loans, dividends or otherwise. Our subsidiaries are not obligated to make funds available to us for payment of our debt securities or otherwise. In addition, their ability to make any payments will depend on their earnings, the terms of their indebtedness, business and tax considerations and legal restrictions. The Notes effectively rank junior to all liabilities of our subsidiaries. In the event of a bankruptcy, liquidation or dissolution of a subsidiary and following payment of its liabilities, the subsidiary may not have sufficient assets remaining to make payments to us as a stockholder or otherwise. The Indenture does not limit the amount of unsecured debt which our subsidiaries may incur. In addition, we and our subsidiaries may incur secured debt and enter into sale and leaseback transactions, subject to certain limitations. See “Description of Notes—Certain Covenants.”

The Notes will not restrict our ability to incur additional debt, to repurchase outstanding securities or to take other actions that could negatively impact our ability to satisfy our respective obligations under the Notes.

Neither the Notes nor the Indenture governing the Notes will restrict our ability or the ability of our subsidiaries to incur additional debt, repurchase securities, recapitalize, or pay dividends or make distributions to shareholders, or require us to maintain interest coverage or other current ratios. Although the Indenture governing the Notes will contain limited covenants that would restrict our ability and the ability of our subsidiaries to incur certain secured indebtedness, these restrictions only apply to the extent that the indebtedness incurred is secured by a lien on the Capital Stock of any of our Significant Subsidiaries (as defined in the Indenture).

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Other than as described above and under the caption “Description of Notes—Repurchase Upon a Change of Control” below, the provisions of the Indenture governing the Notes will not afford holders of debt securities issued thereunder, including the Notes, protection in the event of a sudden or significant decline in our credit quality or in the event of a takeover, recapitalization or highly leveraged or similar transaction involving us or any of our affiliates that may adversely affect such holders. In addition, our ability to recapitalize, incur additional debt and take a number of other actions that will not be limited by the terms of the Notes or the Indenture could have the effect of diminishing our ability to make payments on the Notes when due.

The Notes will not be guaranteed by any of our subsidiaries.

The Notes will be our general unsecured obligations and will not be guaranteed by any of our subsidiaries. Accordingly, claims of holders of the Notes will be structurally subordinated to the claims of creditors of these subsidiaries, including trade creditors. All obligations of these subsidiaries will have to be satisfied before any of the assets of such subsidiaries would be available for distribution, upon a liquidation or otherwise, to us to satisfy our obligations under the Notes. In addition, the Indenture governing the Notes will not prohibit our subsidiaries from incurring additional indebtedness.

As of September 30, 2024, our subsidiaries had approximately $262.0 million of indebtedness (excluding, intercompany liabilities) to which the Notes would have been structurally subordinated.

The Notes will be unsecured and therefore will be effectively subordinated to our future secured debt, if any.

The Notes will not be secured. As of September 30, 2024, we had no secured indebtedness outstanding. The Notes will be effectively subordinated to any secured indebtedness we incur in the future to the extent of the value of the assets securing such indebtedness. In the event of our bankruptcy, liquidation, reorganization or other winding up, our assets that secure such debt will be available to pay obligations on the Notes only after the secured debt has been repaid in full from these assets. There may not be sufficient assets remaining to pay amounts due on any or all of the Notes then outstanding.

Changes in our credit ratings may adversely affect your investment in the Notes.

The ratings of debt rating agencies assigned to the Notes are not recommendations to purchase, hold or sell the Notes, inasmuch as the ratings do not comment as to market prices or suitability for a particular investor, are limited in scope, and do not address all material risks relating to an investment in the Notes, but rather reflect only the view of each rating agency at the time the rating is issued. The ratings are based on current information furnished to the rating agencies by us and information obtained by the rating agencies from other sources. An explanation of the significance of such ratings may be obtained from such rating agency. There can be no assurance that such credit ratings will remain in effect for any given period of time or that such ratings will not be lowered, suspended or withdrawn entirely by the rating agencies, if, in each rating agency’s judgment, circumstances so warrant. Actual or anticipated changes or downgrades in our credit ratings, including any announcement that our ratings are under further review for a downgrade, could affect the market value and liquidity of the Notes and increase our corporate borrowing costs.

A liquid trading market for the Notes may not develop.

There may be no trading market for the Notes. We have been advised by the underwriters for this offering that they presently intend to make a market in the Notes after the consummation of the offering contemplated by this prospectus supplement, although they are under no obligation to do so and may discontinue any market-making activities at any time without any notice. The liquidity of any market for the Notes will depend upon the number of holders of those Notes, our performance, the market for similar securities, the interest of securities dealers in making a market in those Notes and other factors. A liquid trading market may not develop for the Notes. As a result, the market price of the Notes could be adversely affected.

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We may not be able to repurchase the Notes upon a change of control.

Under certain circumstances, and upon the occurrence of specific kinds of change of control events accompanied by a ratings decline with respect to the Notes, we will be required to offer to repurchase all outstanding Notes at 101% of their principal amount plus accrued and unpaid interest, unless we had previously exercised our right to redeem the Notes. If we experience such a change of control and rating decline, we cannot assure you that we would have sufficient financial resources available to satisfy our obligations to repurchase such Notes. Our failure to purchase the Notes as required under the terms of the Notes would result in a default under the Indenture, which could have material adverse consequences for us and the holders of the Notes. See “Description of Notes—Purchase of Notes Upon a Change of Control Triggering Event.”

We have not identified any specific use of the net proceeds of this offering in the event the Transaction does not close.

Consummation of the Transaction is subject to a number of conditions and, if the Purchase Agreement is terminated for any reason, our board of directors and management will have broad discretion over the use of the net proceeds we receive in this offering. Since the primary purpose of this offering is to provide funds to pay a portion of the Transaction consideration, we have not identified a specific use for the net proceeds in the event the Transaction does not occur. Any funds received may be used by us for general corporate purposes, which may include other acquisitions, repayment of outstanding indebtedness, capital expenditures, working capital and stock repurchases. The failure of our management to use the net proceeds from this offering effectively could have an adverse effect on our business.

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USE OF PROCEEDS

We estimate that the net proceeds from this offering, after deducting the underwriting discount and estimated offering expenses, will be approximately $     .

We expect to use the net proceeds of this offering to fund a portion of the cash consideration payable in connection with the Transaction and, to the extent that any proceeds remain thereafter, or if the Transaction is not completed, for general corporate purposes, including other acquisitions. In addition to the net proceeds from this offering, we expect to use available cash, including any cash raised in the Common Stock Offering, and available borrowings under our Revolving Credit Facility or other borrowings to complete the Transaction.

This offering is not conditioned on the closing of the Transaction or the concurrent Common Stock Offering, and there can be no assurance that the Transaction will be completed. The closing of the concurrent Common Stock Offering is not conditioned on the closing of this offering or the closing of the Transaction. The Notes offered hereby will remain outstanding whether or not the Transaction is completed, other than in the event of a Special Optional Redemption. See “Description of Notes—Special Optional Redemption upon a Transaction Termination Event” for more information.

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DESCRIPTION OF NOTES

The following is a description of the material terms of the Notes offered pursuant to this prospectus supplement. This description supplements the disclosure set forth in the accompanying prospectus under “Description of Securities.”

The Notes will be issued under an indenture, dated as of May 20, 2021 (the “Indenture”), by and between the Company and The Bank of New York Mellon Trust Company, N.A., as trustee (the “trustee”). The following statements with respect to the Notes are summaries of the provisions of the Notes and the Indenture. We urge you to read such documents in their entirety because they, and not this description, will define your rights as holders of the Notes. A copy of the form of Indenture is filed as an exhibit to the registration statement of which this prospectus supplement and the accompanying prospectus are a part.

General

The Company will issue the 2027 Notes in an initial principal amount of $      , the 2029 Notes in an initial principal amount of $      , the 2032 Notes in an initial principal amount of $      , the 2035 Notes in an initial principal amount of $       and the 2055 Notes in an initial principal amount of $      . As described under “—Further Issuances,” under the Indenture the Company can issue additional Notes of any series at later dates. In addition, the Company can issue additional series of debt securities without limitation as to aggregate principal amount under the Indenture in the future.

The Notes will be issued only in registered form without coupons in denominations of $2,000 and any integral multiple of $1,000 above that amount. The Notes will be represented by global certificates registered in the name of a nominee of The Depository Trust Company, which we refer to in this prospectus supplement as DTC, as described under “—Book-Entry, Delivery and Form.”

The trustee, through its corporate trust office, will act as the Issuer’s paying agent and security registrar in respect of the Notes. The current location of such corporate trust office for such purposes is The Bank of New York Mellon Trust Company, N.A., 2 North LaSalle Street, 7th Floor, Chicago, Illinois 60602. So long as the Notes are issued in the form of global certificates, payments of principal, interest and premium, if any, will be made by the Company through the paying agent to DTC.

The Notes will not be entitled to the benefit of any sinking fund other than in the event of a Special Optional Redemption. See “—Special Optional Redemption upon a Transaction Termination Event” below for more information.

Payments

The 2027 Notes will mature on    , 2027; the 2029 Notes will mature on    , 2029; the 2032 Notes will mature on    , 2032; the 2035 Notes will mature on    , 2035; and the 2055 Notes will mature on    , 2055.

Interest on the 2027 Notes and the 2029 Notes is payable semi-annually in arrears on    and     of each year, beginning on    , 2025. Interest on the 2032 Notes, the 2035 Notes and the 2055 Notes is payable semi-annually in arrears on    and     of each year, beginning on    , 2025.

The Company will pay interest to those persons who were holders of record of the 2027 Notes and the 2029 Notes on    or    (whether or not a business day) immediately preceding the applicable interest payment date. The Company will pay interest to those persons who were holders of record of the 2032 Notes, the 2035 Notes and the 2055 Notes on    or    (whether or not a business day) immediately preceding the applicable interest payment date. Interest on the Notes will accrue from the date of original issuance or, if interest has already been paid, or duly provided for, from the date it was most recently paid or duly provided for. Interest will be computed on the basis of a 360-day year comprised of twelve 30-day months.

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If any interest payment date or the maturity date of the Notes is not a business day, then the related payment of interest and/or principal on such date will be paid on the next succeeding business day with the same force and effect as if made on such interest payment date or maturity date and no further interest will accrue in respect of the delay. “Business day” means, with respect to the Notes, each Monday, Tuesday, Wednesday, Thursday and Friday which is not a day on which banking institutions in the Borough of Manhattan, New York City are authorized or obligated by law or executive order to close.

Further Issuances

The Company may, from time to time, without notice to or the consent of the holders of the Notes, issue additional Notes of either series under the Indenture, in which case any additional Notes of such series so issued will have the same form and terms (other than the date of issuance and the public offering price and, under certain circumstances, the date from which interest thereon will begin to accrue and the initial interest payment date), and such additional Notes of the applicable series will form a single series with the previously issued Notes of such series, including for voting purposes; provided that unless such additional Notes are issued in a “qualified reopening” of or otherwise part of the same “issue” as the previously issued Notes, or are issued with less than a de minimis amount of OID, in each case, for U.S. federal income tax purposes, such additional Notes will be issued with a different CUSIP, ISIN, Common Code and/or other securities identifier than the identifier used for such previously issued Notes.

Ranking

The Notes are senior unsubordinated unsecured obligations of the Company and will:

• rank equally with all of the Company’s existing and future unsubordinated and unsecured debt;

• be senior in right of payment to all of the Company’s existing and future subordinated debt;

• be effectively subordinated to all of the Company’s existing and future secured debt, to the extent of the value of the assets securing such debt; and

• be structurally subordinated to all existing and future liabilities of the Company’s subsidiaries, including any claims of trade creditors.

As of September 30, 2024, the Company had approximately $4,550.0 million of outstanding senior indebtedness that would rank equally with the Notes. As of September 30, 2024, the Company had no secured indebtedness outstanding.

The Company has only a stockholder’s claim on the assets of its subsidiaries. This stockholder’s claim is junior to the claims that creditors of such subsidiaries have against those subsidiaries. Holders of the Notes will be creditors only of the Company and not creditors of the Company’s subsidiaries. As a result, all of the existing and future liabilities of the Company’s subsidiaries, including any claims of trade creditors, will be structurally senior to the Notes.

The Company’s subsidiaries have other liabilities, including contingent liabilities that may be significant. The Indenture does not contain any limitations on the amount of additional debt that the Company may incur (other than certain debt secured by liens on the Capital Stock of Significant Subsidiaries) or on the amount of additional debt that the Company’s subsidiaries may incur. The amounts of this debt could be substantial, and this debt may be debt of the Company’s subsidiaries, in which case this debt would be effectively senior in right of payment to the Notes. As of September 30, 2024, the Company’s subsidiaries had approximately $262.0 million of indebtedness (excluding, intercompany liabilities) to which the Notes would have been structurally subordinated.

The Notes are obligations exclusively of the Company. Substantially all of its operations are conducted through its subsidiaries. Therefore, the Company’s ability to service its debt, including the Notes, is dependent

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upon the earnings of its subsidiaries and their ability to distribute those earnings as dividends, loans or other payments to the Company. Certain laws restrict the ability of these subsidiaries to pay dividends and make loans and advances to the Company. In addition, such subsidiaries may enter into contractual arrangements that limit their ability to pay dividends and make loans and advances to the Company.

Special Optional Redemption upon a Transaction Termination Event

We expect to use the net proceeds from this offering in connection with the Transaction, as described under “Use of Proceeds.” The closing of this offering is expected to occur prior to the consummation of the Transaction. We may, at our option, redeem, in whole and not in part, any or all series of Notes by providing notice of such redemption to the holders of the series of Notes being redeemed, within 30 days following a Transaction Termination Event (as defined below), at a redemption price equal to 101% of the aggregate principal amount of the series of Notes being redeemed, plus accrued and unpaid interest, if any, to, but excluding, the redemption date.

A Transaction Termination Event will have occurred if:

(1) on or prior to March 9, 2026 (the “Transaction Deadline”),

(a) the Transaction is not consummated, or

(b) the Company has publicly announced that the Transaction will not be consummated; or

(2) if prior to the Transaction Deadline, the Purchase Agreement is terminated, other than in connection with the consummation of the Transaction,

provided, that if the Purchase Agreement is amended to extend the date by which the Transaction must be consummated, the Transaction Deadline will be extended to the same date, but in no event will the Transaction Deadline be extended beyond July 7, 2026. The trustee shall not be charged with knowledge of, or responsible for monitoring whether, a Transaction Termination Event has occurred.

If within 30 days after the occurrence of a Transaction Termination Event, the Company elects not to redeem a series of Notes, or if the Company notifies holders of its election to redeem a series of Notes within such 30-day period but does not consummate the redemption on the date fixed for such redemption, the interest rate on such series of Notes will increase by 2.50% beginning on (and including) the first day of the interest period following the interest period in which the Transaction Termination Event occurred until the maturity date of that series of Notes. If the interest rate on a series of Notes is increased as described in this paragraph, the term “interest,” as used with respect to those Notes, will be deemed to include any such additional interest unless the context otherwise requires. Neither the trustee nor the paying agent shall be responsible for monitoring whether the interest rate for the Notes has, or should have, increased, and in all cases, the trustee shall be fully protected in relying upon notification by the Company to the Trustee of any such change in the interest rate.

Our actions and determinations in determining the redemption price shall be conclusive and binding for all purposes, absent manifest error. We will notify the trustee of the redemption price promptly after the calculation thereof and the trustee shall have no duty to determine, or verify the calculation of, the redemption price.

Notice of any redemption will be mailed or electronically delivered (or otherwise transmitted in accordance with the depositary’s procedures) at least 10 days but not more than 60 days before the redemption date to each holder the Notes to be redeemed, with a copy to the trustee.

Unless we default in payment of the redemption price, on and after the redemption date of the applicable series of Notes, interest will cease to accrue on such Notes or any portions thereof called for redemption.

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Optional Redemption

Prior to the applicable Par Call Date, each series of Notes will be redeemable in whole at any time or in part from time to time, at our option, at a redemption price (expressed as a percentage of principal amount and rounded to three decimal places) as calculated by us equal to the greater of:

(1) (a) the sum of the present values of the remaining scheduled payments of principal and interest thereon discounted to the redemption date (assuming the Notes matured on the applicable Par Call Date) on a semi-annual basis (assuming a 360-day year consisting of twelve 30-day months) at the applicable Treasury Rate plus  basis points, in the case of the 2027 Notes;  basis points, in the case of the 2029 Notes;   basis points, in the case of the 2032 Notes;   basis points, in the case of the 2035 Notes; and  basis points, in the case of the 2055 Notes, less (b) interest accrued to the date of redemption; and

(2) 100% of the principal amount of the Notes to be redeemed;

plus, in either case, accrued and unpaid interest, if any, to, but excluding, the redemption date.

On or after the applicable Par Call Date, we may redeem the Notes of each series, in whole or in part, at any time and from time to time, at a redemption price equal to 100% of the principal amount of the Notes being redeemed, plus accrued and unpaid interest, if any, to, but excluding, the redemption date.

“Par Call Date” means, with respect to the 2027 Notes,    , 20  ( months prior to the maturity date of the 2027 Notes); with respect to the 2029 Notes,    20  ( months prior to the maturity of the 2029 Notes); with respect to the 2032 Notes,    20  ( months prior to the maturity of the 2032 Notes); with respect to the 2035 Notes,    20  ( months prior to the maturity of the 2035 Notes); and with respect to the 2055 Notes,    20  ( months prior to the maturity of the 2055 Notes).

“Treasury Rate” means, with respect to any redemption date for any Notes of a series, the yield determined by us in accordance with the following two paragraphs.

The Treasury Rate applicable to such redemption shall be determined by us after 4:15 p.m., New York City time (or after such time as yields on U.S. government securities are posted daily by the Board of Governors of the Federal Reserve System), on the third business day preceding the redemption date based upon the yield or yields for the most recent day that appear after such time on such day in the most recent statistical release published by the Board of Governors of the Federal Reserve System designated as “Selected Interest Rates (Daily)—H.15” (or any successor designation or publication) (“H.15”) under the caption “U.S. government securities—Treasury constant maturities—Nominal” (or any successor caption or heading) (“H.15 TCM”). In determining the applicable Treasury Rate, the Company shall select, as applicable: (1) the yield for the Treasury constant maturity on H.15 exactly equal to the period from the redemption date to the applicable Par Call Date (the “Remaining Life”); or (2) if there is no such Treasury constant maturity on H.15 exactly equal to the Remaining Life, the two yields—one yield corresponding to the Treasury constant maturity on H.15 immediately shorter than and one yield corresponding to the Treasury constant maturity on H.15 immediately longer than the Remaining Life—and shall interpolate to the applicable Par Call Date on a straight-line basis (using the actual number of days) using such yields and rounding the result to three decimal places; or (3) if there is no such Treasury constant maturity on H.15 shorter than or longer than the Remaining Life, the yield for the single Treasury constant maturity on H.15 closest to the Remaining Life. For purposes of this paragraph, the applicable Treasury constant maturity or maturities on H.15 shall be deemed to have a maturity date equal to the relevant number of months or years, as applicable, of such Treasury constant maturity from the redemption date.

If on the third business day preceding the redemption date H.15 TCM is no longer published, we shall calculate the Treasury Rate applicable to such redemption based on the rate per annum equal to the semi-annual

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equivalent yield to maturity at 11:00 a.m., New York City time, on the second business day preceding such redemption date of the United States Treasury security maturing on, or with a maturity that is closest to, the applicable Par Call Date, as applicable. If there is no United States Treasury security maturing on the applicable Par Call Date but there are two or more United States Treasury securities with a maturity date equally distant from the applicable Par Call Date, one with a maturity date preceding the applicable Par Call Date and one with a maturity date following the applicable Par Call Date, we shall select the United States Treasury security with a maturity date preceding the applicable Par Call Date. If there are two or more United States Treasury securities maturing on the applicable Par Call Date or two or more United States Treasury securities meeting the criteria of the preceding sentence, we shall select from among these two or more United States Treasury securities the United States Treasury security that is trading closest to par based upon the average of the bid and asked prices for such United States Treasury securities at 11:00 a.m., New York City time. In determining the Treasury Rate in accordance with the terms of this paragraph, the semi-annual yield to maturity of the applicable United States Treasury security shall be based upon the average of the bid and asked prices, expressed as a percentage of principal amount, at 11:00 a.m., New York City time, of such United States Treasury security, and rounded to three decimal places.

Our actions and determinations in determining the redemption price shall be conclusive and binding for all purposes, absent manifest error. We will notify the trustee of the redemption price promptly after the calculation thereof and the trustee shall have no duty to determine, or verify the calculation of, the redemption price.

Notice of any redemption will be mailed or electronically delivered (or otherwise transmitted in accordance with the depositary’s procedures) at least 10 days but not more than 60 days before the redemption date to each holder of Notes to be redeemed, with a copy to the trustee.

In the case of a partial redemption of a series of Notes, selection of certificated Notes of such series for redemption will be made by lot. No Notes of a principal amount of $2,000 or less will be redeemed in part. If any certificated note of a series is to be redeemed in part only, the notice of redemption that relates to such note of such series will state the portion of the principal amount of the Note of such series to be redeemed. A new certificated Note of such series in a principal amount equal to the unredeemed portion of such Note of such series will be issued in the name of the holder of such note upon surrender for cancellation of the original certificated note. For so long as the Notes are held by DTC (or another depositary), the redemption of the Notes shall be done in accordance with the policies and procedures of DTC (or such other depositary).

Unless we default in payment of the redemption price, on and after the redemption date of Notes of a series, interest will cease to accrue on such Notes or any portions thereof called for redemption.

Notice of any redemption of Notes in connection with a transaction or an event may, at our discretion, be given prior to the completion or the occurrence thereof. Any redemption or notice may, at our discretion, be subject to one or more conditions precedent, including, but not limited to, completion or occurrence of a related transaction or event. At our discretion, the redemption date may be delayed until such time as any or all such conditions shall be satisfied, or such redemption may not occur and such notice may be rescinded in the event that any or all such conditions shall not have been satisfied by the redemption date, or by the redemption date as so delayed. We will provide written notice to the trustee as soon as practicable but in any event no later than two days prior to the redemption date if any such redemption has been rescinded or delayed, and upon receipt and at our request the trustee will provide such notice to each holder of the Notes to be redeemed in the same manner in which the notice of redemption was given.

Purchase of Notes Upon a Change of Control Triggering Event

If a Change of Control Triggering Event occurs, unless the Company has exercised its right to redeem the Notes as described above under the heading “—Optional Redemption,” the Company will make an offer to each holder of Notes of either series to repurchase all of that holder’s Notes at a repurchase price in cash equal to

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101% of the aggregate principal amount of Notes repurchased (such principal amount to be equal to $2,000 or an integral multiple of $1,000 in excess thereof), plus any accrued and unpaid interest on the Notes repurchased to, but excluding, the date of repurchase. Within 30 days following any Change of Control Triggering Event or, at the Company’s option, prior to any Change of Control, but after the public announcement of the Change of Control, the Company will send a notice to each holder and the trustee describing the transaction or transactions that constitute or may constitute the Change of Control Triggering Event and offering to repurchase Notes on the payment date specified in the notice, which date will be no earlier than 30 days and no later than 45 days from the date such notice is sent. The notice shall, if sent prior to the date of consummation of the Change of Control, state that the offer to repurchase is conditioned on the Change of Control Triggering Event occurring on or prior to the payment date specified in the notice.

The Company will comply with the requirements of Rule 14e-1 under the Securities Exchange Act of 1934, as amended (the “Exchange Act”) and any other securities laws and regulations to the extent those laws and regulations are applicable in connection with the repurchase of the Notes as a result of a Change of Control Triggering Event. To the extent that the provisions of any securities laws or regulations conflict with the Change of Control Triggering Event provisions of the Notes, the Company will comply with the applicable securities laws and regulations and will not be deemed to have breached its obligations under the Change of Control Triggering Event provisions of the Notes by virtue of such conflict.

On the Change of Control Triggering Event payment date, the Company will, to the extent lawful:

(1) accept for payment all Notes or portions of Notes properly tendered pursuant to the Company’s offer;

(2) deposit with the paying agent an amount equal to the aggregate purchase price in respect of all Notes or portions of Notes properly tendered; and

(3) deliver or cause to be delivered to the trustee, the Notes properly accepted, together with an officers’ certificate stating the aggregate principal amount of Notes being purchased by the Company.

The paying agent will promptly pay, from funds deposited by the Company for such purpose, to each holder of Notes properly tendered the purchase price for the Notes, and the trustee will promptly authenticate and send (or cause to be transferred by book-entry) to each holder a new note equal in principal amount to any unpurchased portion of any Notes surrendered.

The Company will not be required to make an offer to repurchase the Notes upon a Change of Control Triggering Event if a third party makes an offer in the manner, at the times and otherwise in compliance with the requirements for an offer made by the Company and such third party purchases all Notes properly tendered and not withdrawn under its offer.

Certain Covenants

Limitation on Liens

The Indenture provides that the Company shall not, and shall not permit any of its subsidiaries to, directly or indirectly, incur or suffer to exist, any Lien, other than a Permitted Lien, securing Debt upon any Capital Stock of any Significant Subsidiary of the Company that is owned, directly or indirectly, by the Company or any of its subsidiaries, in each case whether owned at the date of the original issuance of the Notes or thereafter acquired, unless it has made or will make effective provision whereby the Notes will be secured by such Lien equally and ratably with (or prior to) all other Debt of the Company or any subsidiary secured by such Lien. Any Lien created for the benefit of the holders of the Notes pursuant to the preceding sentence shall provide by its terms that such Lien will be automatically and unconditionally released and discharged upon release and discharge of the Lien.

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Merger, Consolidation or Sale of Assets

The Company, without the consent of any holder of outstanding Notes, may consolidate with or merge into any other person, or convey, transfer or lease its properties and assets substantially as an entirety to, any person; provided that:

(1) either (x) the Company is the continuing corporation or (y) the person formed by such consolidation or into which the Company is merged or the person which acquires by conveyance or transfer or which leases the properties and assets of the Company, as the case may be, substantially as an entirety:

(a) is organized under the laws of any United States jurisdiction, any state thereof or the District of Columbia; and

(b) expressly assumes the Company’s obligations on the Notes and under the Indenture; and

(2) after giving effect to the transaction, no event of default shall have happened and be continuing.

Events of Default

Each of the following constitutes an event of default with respect to a series of Notes under the Indenture:

• a default in payment of interest on such series of Notes when due continued for 30 days;

• a default in the payment of the principal of or premium, if any, on such series of Notes when due (whether at maturity, upon acceleration, redemption or otherwise);

• a default in the performance, or breach, of any other covenant of the Company (other than a covenant a default in whose performance or whose breach is elsewhere dealt with or which has been included in the Indenture solely for the benefit of debt securities other than such series of the Notes) continued for 90 days after written notice from the trustee to the Company or from the holders of 25% or more in principal amount of the Notes outstanding to the Company and the trustee, respectively;

• a default under any Debt by the Company or any of its respective subsidiaries that results in acceleration of the maturity of such Debt, or failure to pay any such Debt at maturity, in an aggregate amount greater than $175 million or its foreign currency equivalent at the time, provided that the cure of such default shall remedy such Event of Default under this clause; and

• certain events of bankruptcy, insolvency or reorganization.

If an event of default with respect to any series of Notes shall occur and be continuing, the trustee or the holders of not less than 25% in principal amount of such series of Notes then outstanding (with notice to the trustee) may declare the unpaid principal balance immediately due and payable. Notwithstanding the foregoing, in the case an event of default arising from certain events of bankruptcy, insolvency or reorganization, all outstanding Notes will become due and payable immediately without further action or notice. However, any time after a declaration of acceleration with respect to the Notes of any series has been made and before a judgment or decree for payment of the money due has been obtained, the holders of a majority in principal amount of outstanding Notes of such series may, by written notice rescind and annul such acceleration under certain circumstances. See “—Modification and Waiver” below.

The Company must file annually with the trustee an officers’ certificate stating whether or not it is in default in the performance and observance of any of the terms, provisions and conditions of the Indenture and, if so, specifying the nature and status of the default.

Within 90 days after receipt of written notice of any default hereunder with respect to the Notes, the Trustee shall send to all holders notice of such default, unless such default has been cured or waived; but in the case of a default other than in respect of the payment of the principal of or interest on the Notes, the trustee shall be protected in withholding such notice if it in good faith determines that the withholding of such notice is in the interests of the holders of the Notes.

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Modification and Waiver

Modification and amendments of the Indenture may be made by the Company and the trustee with the consent of the holders of a majority in principal amount of the outstanding Notes of each series affected provided, that no modification or amendment may, without the consent of the holder of each outstanding Note of such series affected:

• change the stated maturity of the principal of, or any installment of principal of, or interest on, the Notes of such series;

• reduce the principal amount of, or any premium or interest on, the Notes of such series;

• reduce the amount of principal of the Notes payable upon acceleration of the maturity thereof;

• impair the right to commence suit for the enforcement of any payment on or after the stated maturity thereof (or, in the case of redemption, on or after the Redemption Date) with respect to the Notes of such series;

• reduce the percentage in principal amount of outstanding Notes of such series, the consent of the holders of which is required for modification or amendment of the Indenture or for waiver of compliance with certain provisions of the Indenture or for waiver of certain defaults; or

• modify the modification and waiver provisions of the Indenture, except to increase any percentage consent required or to provide that certain other provisions of the Indenture cannot be modified or waived without the consent of the holder of each Note affected thereby.

Without the consent of any holder of outstanding Notes, the Company and the trustee may amend or supplement the Indenture and each series of Notes to evidence the succession of another person to the Company and the assumption of such successor to the obligations thereof in accordance with the Indenture, to add to the covenants of the Company for the benefit of the holders of all or any series, to surrender any right or power conferred upon the Company, to add any additional events of default, to secure the Notes, to establish the form or terms of any new series of notes, to cure any ambiguity, defect or inconsistency, to provide for the Notes in bearer form in addition to or in place of registered debt securities or to make any other provisions that do not adversely affect the rights of any holder of outstanding debt securities in any material respect.

The holders of a majority in principal amount of the outstanding debt securities of any series may on behalf of the holders of all debt securities of that series waive any past default under the Indenture with respect to that series and its consequences with respect to that series, except a default in the payment of the principal of (or premium, if any) or interest on any debt security of that series or in respect of a provision which under such Indenture cannot be modified or amended without the consent of the holder of each outstanding debt security of that series.

Satisfaction and Discharge of Indenture; Defeasance

The Indenture with respect to the Notes of any series may be discharged, subject to the terms and conditions as specified herein when:

• all Notes of that series, with the exceptions provided for in the Indenture, of that series have been delivered to the trustee for cancellation;

• all Notes not theretofore delivered to the trustee for cancellation:

• have become due and payable; or

• will become due and payable at their stated maturity within one year; or

• are to be called for redemption within one year; or

• certain events or conditions occur as specified in the Indenture.

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The Company can terminate all of its obligations under the Indenture with respect to the Notes of any series, other than the obligation to pay interest on, premium, if any, and the principal of the Notes of such series and certain other obligations, known as “covenant defeasance,” at any time by:

• depositing money or U.S. government obligations with the trustee in an amount sufficient in the written opinion of a nationally recognized firm of public accountants to pay the principal of and interest on the Notes of such series to their maturity; and

• complying with certain other conditions, including delivery to the trustee of an opinion of counsel to the effect that holders and beneficial owners of the Notes of such series will not recognize income, gain or loss for U.S. federal income tax purposes as a result of such covenant defeasance and will be subject to U.S. federal income tax on the same amounts in the same manner and at the same times as would have been the case if such covenant defeasance had not occurred.

In addition, the Company can terminate all of its obligations under the Indenture with respect to the Notes of any series, including the obligation to pay interest on, premium, if any, and the principal of the Notes of such series, known as “legal defeasance”, at any time by:

• depositing money or U.S. government obligations with the trustee in an amount sufficient in the written opinion of a nationally recognized firm of public accountants to pay the principal of and interest on the Notes of such series to their maturity, and

• complying with certain other conditions, including delivery to the trustee of an opinion of counsel stating that (x) there has been a change in the U.S. federal income tax law since the date of the issuance of the Notes or (y) the Company has received from, or there has been published by, the U.S. Internal Revenue Service a ruling or other formal statement or action, in either case, to the effect that holders and beneficial owners of Notes of such series will not recognize income, gain or loss for U.S. federal income tax purposes as a result of such legal defeasance and will be subject to U.S. federal income tax on the same amounts, in the same manner and at the same times as would have been the case if such legal defeasance had not occurred.

Regarding the Trustee

The Indenture provides that, except during the continuance of an event of default known to the trustee, the trustee will perform only such duties as are specifically set forth in the Indenture. During the existence of an event of default known to the trustee, the trustee will exercise such rights and powers vested in it under the Indenture and use the same degree of care and skill in its exercise as a prudent person would exercise under the circumstances in the conduct of such person’s own affairs.

The Indenture and provisions of the Trust Indenture Act of 1939, as amended (the “Trust Indenture Act”) that are incorporated by reference therein contain limitations on the rights of the trustee, should it become one of the Company’s creditors, to obtain payment of claims in certain cases or to realize on certain property received by it in respect of any such claim as security or otherwise. The trustee is permitted to engage in other transactions with the Company or any of its affiliates; provided, however, that if it acquires any conflicting interest (as defined in the Indenture or in the Trust Indenture Act), it must eliminate such conflict or resign, subject to its right under the Trust Indenture Act to seek a stay of its duty to resign.

The Indenture also provides the trustee with certain rights and privileges.

Governing Law

The Indenture is and the Notes will be governed by and construed in accordance with the laws of the State of New York.

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Book-Entry, Delivery and Form

DTC, New York, NY, will act as securities depository for the Notes. The Notes will be issued as fully registered Global Securities registered in the name of Cede & Co. (DTC’s partnership nominee) or such other name as may be requested by an authorized representative of DTC.

Beneficial interests in the Notes will be shown on, and transfers thereof will be effected only through, records maintained by DTC and its direct and indirect participants. Investors may elect to hold interests in the Notes through DTC if they are participants in the DTC system, or indirectly through organizations which are participants in the DTC system.

DTC has informed us that DTC is:

• a limited-purpose trust company organized under the laws of the State of New York;

• a “banking organization” within the meaning of the New York banking law;

• a member of the Federal Reserve System;

• a “clearing corporation” within the meaning of the New York Uniform Commercial Code; and

• a “clearing agency” registered pursuant to the provisions of Section 17A of the Exchange Act.

DTC holds securities that its participants, which we refer to in this prospectus supplement as the Direct Participants, deposit with DTC. DTC also facilitates the settlement among Direct Participants of securities transactions, such as transfers and pledges, in deposited securities through electronic computerized book-entry changes in Direct Participants’ accounts, which eliminates the need for physical movement of securities certificates. Direct Participants include securities brokers and dealers, banks, trust companies, clearing corporations, and certain other organizations. DTC is owned by a number of its Direct Participants and by the New York Stock Exchange, Inc., the NYSE MKT LLC, and FINRA. Access to the DTC system is also available to others, which we refer to in this prospectus supplement as Indirect Participants, such as securities brokers and dealers, banks, and trust companies that clear through or maintain a custodial relationship with a Direct Participant, either directly or indirectly. The rules applicable to DTC and its Direct and Indirect Participants are on file with the SEC.

Purchases of the Notes under the DTC system must be made by or through Direct Participants, which receive a credit for the Notes on DTC’s records. The ownership interest of each actual purchaser of each note, which we refer to in this prospectus supplement as the Beneficial Owner, is in turn to be recorded on the Direct and Indirect Participants’ records. Beneficial Owners will not receive written confirmations from DTC of their purchase, but Beneficial Owners are expected to receive written confirmations providing details of the transaction, as well as periodic statements of their holdings, from the Direct or Indirect Participant through which the Beneficial Owner entered into the transaction. Transfers of ownership interests in the Notes are to be accomplished by entries made on the books of Direct and Indirect Participants acting on behalf of Beneficial Owners. Beneficial Owners will not receive certificates representing their ownership interests in Notes except in the event that use of the book-entry system for the Notes is discontinued. As a result, the ability of a person having a beneficial interest in the Notes to pledge such interest to persons or entities that do not participate in the DTC system, or to otherwise take actions with respect to such interest, may be affected by the lack of a physical certificate evidencing such interest. In addition, the laws of some states require that certain persons take physical delivery in definitive form of securities that they own and that security interests in negotiable instruments can only be perfected by delivery of certificates representing the instruments. Consequently, the ability to transfer Notes evidenced by the global Notes will be limited to such extent.

To facilitate subsequent transfers, all Notes deposited by Direct Participants with DTC are registered in the name of DTC’s partnership nominee, Cede & Co. or such other name as may be requested by an authorized representative of DTC. The deposit of Notes with DTC and their registration in the name of Cede & Co. or such

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other nominee do not effect any change in beneficial ownership. DTC has no knowledge of the actual Beneficial Owners of the Notes. DTC’s records reflect only the identity of the Direct Participants to whose accounts such Notes are credited, which may or may not be the Beneficial Owners. The Direct and Indirect Participants will remain responsible for keeping account of their holdings on behalf of their customers.

Conveyance of notices and other communications by DTC to Direct Participants, by Direct Participants to Indirect Participants, and by Direct Participants and Indirect Participants to Beneficial Owners will be governed by arrangements among them, subject to any statutory or regulatory requirements as may be in effect from time to time.

Redemption notices will be sent to DTC. If less than all of the Notes are being redeemed, DTC’s practice is to determine by lot the amount of the interest of each Direct Participant in the Notes to be redeemed.

Neither DTC nor Cede & Co. (nor such other DTC nominee) will consent or vote with respect to the Notes. Under its usual procedures, DTC sends an Omnibus Proxy to the Company as soon as possible after the record date.

The Omnibus Proxy assigns Cede & Co.’s consenting or voting rights to those Direct Participants to whose accounts the Notes are credited on the record date (identified in a listing attached to the Omnibus Proxy).

Payments of principal, interest and premium, if any, on the Notes will be made to Cede & Co., or such other nominee as may be requested by an authorized representative of DTC. DTC’s practice is to credit Direct Participants’ accounts, upon DTC’s receipt of funds and corresponding detail information from the Company on the payable date in accordance with their respective holdings shown on DTC’s records. Payments by Participants to Beneficial Owners will be governed by standing instructions and customary practices, as is the case with securities held for the accounts of customers in bearer form or registered in “street name” and will be the responsibility of such Participant and not of DTC, or the Company, subject to any statutory or regulatory requirements as may be in effect from time to time. Payment of redemption proceeds, distributions, and dividends to Cede & Co. (or such other nominee as may be requested by an authorized representative of DTC) is the Company’s responsibility and disbursement of such payments to Direct Participants will be the responsibility of DTC, and disbursement of such payments to the Beneficial Owners will be the responsibility of Direct and Indirect Participants.

Investors electing to hold their Notes through DTC will follow the settlement practices applicable to U.S. corporate debt obligations. The securities custody accounts of investors will be credited with their holdings on the settlement date against payment in same-day funds within DTC effected in U.S. dollars.

Secondary market sales of book-entry interests in the Notes between DTC Participants will occur in the ordinary way in accordance with DTC rules and will be settled using the procedures applicable to United States corporate debt obligations in DTC’s Settlement System. If DTC is at any time unwilling, unable or ineligible to continue as depository and a successor depository is not appointed by the Company within 90 days, the Company will issue individual Notes in exchange for the Global Security representing such Notes. In addition, the Company may, at any time and in its sole discretion and subject to DTC’s procedures, determine not to have the Notes represented by one or more Global Securities and, in such event, will issue individual Notes in exchange for the Global Security or Securities representing the Notes. Also, if an event of default with respect to the Notes shall have occurred and be continuing, the Company may, and upon the request of the trustee, shall execute, Notes in definitive form in exchange for the Global Security or Securities representing the Notes. Individual Notes will be issued in denominations of $2,000 and any integral multiple of $1,000 above that amount.

Neither the Company nor the trustee will have any responsibility or obligation to participants in the DTC system or the persons for whom they act as nominees with respect to the accuracy of the records of DTC, its nominee or any Direct or Indirect Participant with respect to any ownership interest in the Notes, or with respect

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to payments to or providing of notice for the Direct Participants, the Indirect Participants or the beneficial owners of the Notes.

The information in this section concerning DTC and its book-entry systems has been obtained from sources that we believe to be reliable. Neither we, the trustee nor the underwriter, dealers or agents are responsible for the accuracy or completeness of this information.

Clearstream and Euroclear

Links have been established among DTC, Clearstream Banking, S.A. (“Clearstream Banking SA”) and Euroclear Bank SA/NV (“Euroclear”) (two international clearing systems that perform functions similar to those that DTC performs in the United States), to facilitate the initial issuance of book-entry securities and cross- market transfers of book-entry securities associated with secondary market trading.

Although DTC, Clearstream Banking SA and Euroclear have agreed to the procedures provided below in order to facilitate transfers, they are under no obligation to perform such procedures, and the procedures may be modified or discontinued at any time.

Clearstream Banking SA and Euroclear will record the ownership interests of their participants in much the same way as DTC, and DTC will record the aggregate ownership of each of the U.S. agents of Clearstream Banking SA and Euroclear, as participants in DTC.

When book-entry securities are to be transferred from the account of a DTC participant to the account of a Clearstream Banking SA participant or a Euroclear participant, the purchaser must send instructions to Clearstream Banking SA or Euroclear through a participant at least one business day prior to settlement.

Clearstream Banking SA or Euroclear, as the case may be, will instruct its U.S. agent to receive book-entry securities against payment. After settlement, Clearstream Banking SA or Euroclear will credit its participant’s account. Credit for the book-entry securities will appear on the next day (European time).

Because settlement is taking place during New York business hours, DTC participants can employ their usual procedures for sending book-entry securities to the relevant U.S. agent acting for the benefit of Clearstream Banking SA or Euroclear participants. The sale proceeds will be available to the DTC seller on the settlement date. Thus, to the DTC participant, a cross market transaction will settle no differently than a trade between two DTC participants.

When a Clearstream Banking SA or Euroclear participant wishes to transfer book-entry securities to a DTC participant, the seller must send instructions to Clearstream Banking SA or Euroclear through a participant at least one business day prior to settlement. In these cases, Clearstream Banking SA or Euroclear will instruct its U.S. agent to transfer the book-entry securities against payment. The payment will then be reflected in the account of the Clearstream Banking SA or Euroclear participant the following day, with the proceeds back-valued to the value date (which would be the preceding day, when settlement occurs in New York). If settlement is not completed on the intended value date (i.e., the trade fails), proceeds credited to the Clearstream Banking SA or Euroclear participant’s account would instead be valued as of the actual settlement date.

Certain Definitions

Set forth below are certain of the defined terms used in the Indenture.

“Capital Stock” means, with respect to any person, any shares or other equivalents (however designated) of any class of corporate stock or partnership interests or any other participations, rights, warrants, options or other interests in the nature of an equity interest in such person, including, without limitation, preferred stock and any debt security convertible or exchangeable into such equity interest.

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“Change of Control” means the occurrence of any of the following:

(1) the direct or indirect sale, transfer, conveyance or other disposition (other than by way of merger or consolidation), in one or a series of related transactions, of all or substantially all of our properties or assets and those of our subsidiaries, taken as a whole, to any “person” or “group” (as those terms are used in Section 13(d) and 14(d) of the Exchange Act), other than us or one or more of our wholly-owned subsidiaries;

(2) the consummation of any transaction (including without limitation, any merger or consolidation) the result of which is that any person (including any “person” (as that term is used in Section 13(d)(3) of the Exchange Act)) becomes the “beneficial owner” (as defined in Rules 13d-3 and 13d-5 under the Exchange Act), directly or indirectly, of Capital Stock representing more than 50% of the aggregate ordinary voting power represented by the issued and outstanding Capital Stock of the Company; or

(3) the adoption of a plan relating to the liquidation or dissolution of the Company.

Notwithstanding the foregoing, a transaction will not be deemed to involve a Change of Control if (1) the Company becomes a direct or indirect wholly-owned subsidiary of a holding company and (2)(A) the direct or indirect holders of the voting Capital Stock of such holding company immediately following that transaction are substantially the same as the holders of the voting Capital Stock of the Company immediately prior to that transaction or (B) immediately following that transaction, no person (including any “person” (as that term is used in Section 13(d)(3) of the Exchange Act)) becomes the “beneficial owner” (as defined in Rules 13d-3 and 13d-5 under the Exchange Act), directly or indirectly, of Capital Stock representing more than 50% of the aggregate ordinary voting power represented by the issued and outstanding Capital Stock of such holding company.

The definition of Change of Control includes a phrase relating to the direct or indirect sale, transfer, conveyance or other disposition (other than by way of merger or consolidation), in one or a series of related transactions, of “all or substantially all” of our properties or assets and those of our subsidiaries, taken as a whole. Although there is a limited body of case law interpreting the phrase “substantially all,” there is no precise established definition of the phrase under applicable law. Accordingly, the ability of a holder of Notes to require the Company to repurchase its Notes as a result of the sale, transfer, conveyance or other disposition of less than all of the properties and assets of the Company and its subsidiaries, taken as a whole, to another person or group may be uncertain.

“Change of Control Triggering Event” means the occurrence of both a Change of Control and a Ratings Decline.

“Debt” means:

(a) the principal of and premium (if any) in respect of any obligation of such person for money borrowed, and any obligation evidenced by Notes, debentures, bonds or other similar instruments for the payment of which such person is responsible or liable;

(b) all obligations of such person as lessee under leases required to be capitalized on the balance sheet of the lessee under generally accepted accounting principles and leases of property or assets made as part of any sale and leaseback transaction entered into by such person;

(c) all obligations of such person issued or assumed as the deferred purchase price of property, all conditional sale obligations of such person and all obligations of such person under any title retention agreement (but excluding trade accounts payable arising in the ordinary course of business);

(d) all obligations of such person for the reimbursement of any obligor on any letter of credit, banker’s acceptance or similar credit transaction;

(e) all obligations of the type referred to in clauses (a) through (d) of other persons and all dividends of other persons for the payment of which, in either case, such person is responsible or liable, directly or indirectly, as obligor, guarantor or otherwise, including by means of any guarantee;

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(f) all obligations of the type referred to in clauses (a) through (d) of other persons secured by any Lien on any property of such person (whether or not such obligation is assumed by such person); and

(g) to the extent not otherwise included in this definition, hedging obligations of such person.

“Investment Grade” means a rating of Baa3 or better by Moody’s (or its equivalent under any successor rating categories of Moody’s) and BBB- or better by S&P (or its equivalent under any successor rating categories of S&P) (or, in each case, if such Rating Agency ceases to rate the Notes for reasons outside the Company’s control, the equivalent investment grade credit rating from any Rating Agency selected by the Company as a replacement Rating Agency).

“Lien” means, with respect to any property of any person, any mortgage or deed of trust, pledge, hypothecation, assignment, deposit arrangement, security interest, lien, charge, encumbrance, preference, priority or other security agreement or preferential arrangement of any kind or nature whatsoever on or with respect to such property (including any capitalized lease obligation, conditional sale or other title retention agreement having substantially the same economic effect as any of the foregoing or any sale and leaseback transaction).

“Moody’s” means Moody’s Investors Service Inc., a subsidiary of Moody’s Corporation, and its successors.

“Permitted Lien” means (i) Liens on the Capital Stock of a Significant Subsidiary to secure Debt incurred to finance the purchase price of such Capital Stock; (ii) Liens on the Capital Stock of a Significant Subsidiary existing at the time such person becomes a Subsidiary, provided that any such Lien is not incurred in anticipation of such person becoming a Subsidiary; and (iii) extensions, renewals, refinancings or replacements of any Lien referred to in the foregoing clauses (i) and (ii); provided, however, that any Liens permitted by any of the foregoing clauses (i) and (ii) shall not extend to or cover any additional Capital Stock of a Significant Subsidiary, other than the property that previously secured such Lien.

“Rating Agency” means:

(1) each of Moody’s and S&P; and

(2) if either of Moody’s or S&P ceases to rate the Notes or fails to make a rating of the Notes publicly available for reasons outside the Company’s control, a “nationally recognized statistical rating organization” within the meaning of Rule 15c3-1(c) (2) (vi) (F) under the Exchange Act selected by the Company as a replacement agency for Moody’s or S&P, or both, as the case may be.

“Ratings Decline” means at any time during the period commencing on the earlier of, (i) the occurrence of a Change of Control or (ii) public notice of the occurrence of a Change of Control or the intention by the Company to effect a Change of Control, and ending 60 days thereafter (which period shall be extended so long as the rating of the Notes is under publicly announced consideration for a possible downgrade by any of the Rating Agencies) that (a) the rating of the Notes shall be reduced by both Rating Agencies and (b) the Notes shall be rated below Investment Grade by each of the Rating Agencies.

“S&P” means S&P Global Ratings, and its successors.

“Significant Subsidiary” means any subsidiary that would be a “Significant Subsidiary” of a specified person within the meaning of Rule 1-02 under Regulation S-X promulgated by the SEC.

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CERTAIN UNITED STATES FEDERAL INCOME TAX CONSEQUENCES

United States Taxation

This section describes certain United States federal income tax consequences of the purchase, ownership and sale, exchange, retirement or other taxable disposal of the Notes offered in this offering. It applies to you only if you are a beneficial owner of the Notes that acquires Notes in this offering at their initial offering price and you hold your Notes as capital assets for United States federal income tax purposes. This section does not address all of the United States federal income tax consequences that may apply to a holder that is subject to special tax rules, such as:

• a dealer in securities or currencies;

• a trader in securities that elects to use a mark-to-market method of accounting for its securities holdings;

• a bank or other financial institution;

• an insurance company;

• a real estate investment trust or regulated investment company;

• a tax-exempt organization;

• a person that owns Notes that are a hedge or that are hedged against interest rate risks;

• a person that owns Notes as part of a straddle or conversion transaction for United States federal income tax purposes;

• “controlled foreign corporations,” “passive foreign investment companies” and corporations that accumulate earnings to avoid United States federal income tax;

• S corporations, partnerships or other entities or arrangements treated as partnerships for United States federal income tax purposes (and investors therein);

• a United States holder (as defined below) whose functional currency for United States federal income tax purposes is not the United States dollar; or

• United States expatriates, certain former citizens or long-term residents of the United States.

This section is based on the Internal Revenue Code of 1986, as amended (the “Code”), its legislative history, existing and proposed regulations under the Code, published rulings and court decisions, all as currently in effect. These authorities are subject to change, possibly on a retroactive basis. In addition, this section does not address all aspects of United States taxation that may be applicable to investors in light of their particular circumstances, including the effect of any alternative minimum tax, the Medicare surtax on certain net investment income, gift or estate tax laws, the special timing rule promulgated under Section 451(b) of the Code, or any state or local tax laws.

If a partnership (including any entity treated as a partnership for United States federal income tax purposes) holds the Notes, the United States federal income tax treatment of a partner will generally depend on the status of the partner and the activities of the partnership. A partner in a partnership holding the Notes should consult its tax advisor with regard to the United States federal income tax treatment of an investment in the Notes.

Please consult your own tax advisor concerning the consequences of purchasing, owning or disposing of the Notes in your particular circumstances under the Code and the laws of any other taxing jurisdiction.

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United States Holders

This subsection describes the United States federal income tax consequences to a United States holder. You are a United States holder if you are a beneficial owner of a Note and you are, for United States federal income tax purposes:

• an individual citizen or resident of the United States;

• a corporation (or other entity taxable as a corporation for United States federal income tax purposes) created or organized in the United States or under the laws of the United States, any state thereof or the District of Columbia;

• an estate whose income is subject to United States federal income tax regardless of its source; or

• a trust if (i) a United States court can exercise primary supervision over the trust’s administration and one or more United States persons are authorized to control all substantial decisions of the trust, or (ii) it was in existence on August 20, 1996 and made a valid election to continue to be treated as a domestic trust.

If you are not a United States holder, this subsection does not apply to you and you should refer to “Non-United States Holders” below.

Additional Payments. In certain circumstances, the Company may be obligated or elect to pay amounts in excess of stated principal on the Notes. See “Description of Notes—Optional Redemption,” “Description of Notes—Special Optional Redemption upon a Transaction Termination Event” and “—Purchase of Notes Upon a Change of Control Triggering Event.” The Company believes that the possibility of any such payment is remote and therefore the rules governing contingent payment debt instruments should not apply to the Notes. The Company’s position is binding on a United States holder unless such holder discloses to the United States Internal Revenue Service (the “IRS”) its contrary position in the manner required by applicable Treasury regulations. The IRS, however, may take a different position, which could require a United States holder to accrue income on its Notes in excess of stated interest and to treat as ordinary income rather than capital gain any income realized on the taxable disposition of a Note. The discussion herein assumes that the Notes will not be treated as contingent payment debt instruments.

Payments of Interest. Interest on a Note will generally be taxable to you as ordinary interest income at the time you receive the interest or when it accrues, depending on your method of accounting for United States federal income tax purposes. It is expected, and this section assumes, that the Notes will be issued without original issue discount (“OID”) for United States federal income tax purposes. In general, however, if the Notes are issued with OID at or above a de minimis threshold, you will be required to include OID in gross income, as ordinary income, under a “constant-yield method” before the receipt of cash attributable to such income, regardless of your regular method of accounting for United States federal income tax purposes.

Sale, Exchange, Retirement or Other Taxable Disposition of the Notes. Your adjusted tax basis in a Note generally will be its cost. Unless a non-recognition provision applies, you will generally recognize capital gain or loss on the sale, exchange, retirement or other taxable disposition of a Note equal to the difference between the amount you realize on such disposition (excluding any amounts attributable to accrued but unpaid interest, which will be taxable as ordinary interest income to the extent not previously included in income) and your adjusted tax basis in the Note. Capital gain of a noncorporate United States holder is generally taxed at a reduced rate of taxation where the holder has a holding period greater than one year. The deductibility of capital losses is subject to certain limitations.

Non-United States Holders

This subsection describes the United States federal income tax consequences to a Non-United States holder. You are a Non-United States holder if you are the beneficial owner of a Note and are not a United States holder

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(as described above) or a partnership (including any entity treated as a partnership) for United States federal income tax purposes.

If you are a United States holder, this subsection does not apply to you and you should refer to “United States Holders” above.

Payments of Interest. Subject to the discussions below under the captions “—Backup Withholding and Information Reporting” and “—FATCA,” the interest income paid to you in respect of the Notes generally will not be subject to United States federal income taxes or United States withholding tax if such income is not effectively connected with the conduct by you of a trade or business in the United States and:

• you do not own, actually or constructively, 10% or more of the total combined voting power of all classes of the Company’s voting equity interests; and

• you are not a “controlled foreign corporation” that is related to the Company actually or constructively through stock ownership; and

• the applicable withholding agent (i) receives a statement (generally on IRS Form W-8BEN or IRS Form W-8BEN-E) from you (or from a financial institution holding the Notes on your behalf in the ordinary course of its business), signed under penalties of perjury, that you are not a United States person and certain other certification requirements are satisfied and (ii) has no actual knowledge or reason to know that you are a United States holder.

If you cannot satisfy the requirements described above, payments of interest made to you will be subject to United States federal withholding tax at a 30% rate, unless (i) you provide the withholding agent with a properly executed IRS Form W-8BEN or IRS Form W-8BEN-E (or applicable successor form) claiming an exemption from (or a reduction of) withholding under the benefits of an applicable income tax treaty, or (ii) the payments of interest are effectively connected with your conduct of a trade or business in the United States (and, if required by an applicable income tax treaty, are attributable to a permanent establishment maintained by you in the United States) and you provide the withholding agent with a properly executed IRS Form W-8ECI.

Interest income that is effectively connected with your conduct of a United States trade or business will be taxed on a net basis at regular graduated United States federal income tax rates rather than the 30% gross rate unless an applicable tax treaty provides otherwise. In the case of a Non-United States holder that is a corporation, branch profits tax at a rate of 30% (or a lower applicable treaty rate) also may apply to the holder’s effectively connected interest, as adjusted for certain items.

Sale, Exchange, Retirement or Other Taxable Disposition of the Notes. Subject to the discussions below under the captions “—Backup Withholding and Information Reporting” any gain you realize on a sale, exchange, retirement or other taxable disposition of the Notes generally will be exempt from United States federal income tax, including United States withholding tax, unless:

• your gain is effectively connected with your conduct of a trade or business in the United States (and, if required by an applicable income tax treaty, is attributable to a United States permanent establishment), in which case such gain would generally be taxed in the same manner as interest that is effectively connected with such trade or business, as described above; or

• you are an individual holder and are present in the United States for 183 days or more in the taxable year of the disposition and certain other conditions are met, in which case, unless an applicable tax treaty provides otherwise, you will generally be subject to a 30% United States federal income tax on any gain recognized, which may be offset by certain United States source losses.

Backup Withholding and Information Reporting

In general, information reporting requirements will apply to payments of interest on a Note, and the proceeds of a sale or other taxable disposition (including a retirement or redemption) of a Note, paid to United

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States holders unless such holders establish that they are exempt recipients. Backup withholding may apply to such payments or proceeds if the United States holder fails to provide a correct taxpayer identification number and otherwise comply with the applicable backup withholding rules.

Non-United States holders that properly certify as to their non-United States status as described above under the third bullet in “—Non-United States Holders—Payments of Interest” or otherwise establish an exemption are not subject to backup withholding on payments of interest to them. However, information returns are required to be filed with the IRS in connection with any interest paid to the Non-United States holder, regardless of whether any tax was actually withheld. Copies of information returns that are filed with the IRS may also be made available under the provisions of an applicable treaty or agreement to the tax authorities of the country in which the Non-United States holder resides or is established. Proceeds of the sale or other taxable disposition (including a retirement or redemption) of a Note within the United States or conducted through certain United States-related brokers generally will not be subject to backup withholding or information reporting if the Non-United States holder complies with certain certification procedures or otherwise establishes an exemption. Proceeds of a disposition (including a retirement or redemption) of a Note conducted through a non-United States office of a non-United States broker (other than a United States-related broker), which proceeds are paid outside the United States, generally will not be subject to backup withholding or information reporting.

Backup withholding is not an additional tax. Any amounts withheld under the backup withholding rules from a payment made to a holder generally may be claimed as a credit against such person’s United States federal income tax liability, if any, and may entitle such person to a refund, provided such holder timely furnishes the required information to the IRS.

FATCA

Under Sections 1471 through 1474 of the Code (such Sections commonly referred to as “FATCA”), a 30% United States federal withholding tax may apply to any interest paid on the Notes to (i) a “foreign financial institution” (as specifically defined in the Code) which does not provide sufficient documentation, typically on IRS Form W-8BEN-E, evidencing either (x) an exemption from FATCA, or (y) its compliance (or deemed compliance) with FATCA (which may alternatively be in the form of compliance with an intergovernmental agreement with the United States) in a manner which avoids withholding, or (ii) a “non-financial foreign entity” (as specifically defined in the Code) which does not provide sufficient documentation, typically on IRS Form W-8BEN-E, evidencing either (x) an exemption from FATCA, or (y) adequate information regarding certain substantial United States beneficial owners of such entity (if any). If an interest payment is both subject to withholding under FATCA and subject to the withholding tax discussed above under “—Non-United States Holders—Payments of Interest,” the withholding under FATCA may be credited against, and therefore reduce, such other withholding tax. You are urged to consult your own tax advisor regarding these rules.

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UNDERWRITING

BofA Securities, Inc. and Morgan Stanley & Co. LLC are acting as representatives of the underwriters named below and joint book-running managers of this offering. Subject to the terms and conditions stated in the underwriting agreement dated the date of this prospectus supplement, each underwriter named below has agreed, severally and not jointly, to purchase from us, and we have agreed to sell to that underwriter, the principal amount of the Notes set forth opposite the underwriter’s name in the table below.

Underwriters	Principal amount of 2027 Notes		Principal amount of 2029 Notes		Principal amount of 2032 Notes		Principal amount of 2035 Notes		Principal amount of 2055 Notes
BofA Securities, Inc.	$		$		$		$		$
Morgan Stanley & Co. LLC
Total	$		$		$		$		$

Subject to terms and conditions set forth in the underwriting agreement, the underwriters are obligated, severally and not jointly, to purchase all the Notes if they purchase any of the Notes. If an underwriter defaults, the underwriting agreement provides that the purchase commitments of the non-defaulting underwriters may be increased or the underwriting agreement may be terminated.

The underwriters are offering the Notes, subject to prior sale, when, as and if issued to and accepted by them, subject to approval of legal matters by their counsel, including the validity of the Notes, and other conditions contained in the underwriting agreement, such as the receipt by the underwriters of officer’s certificates and legal opinions. The underwriters reserve the right to withdraw, cancel or modify offers to the public and to reject orders in whole or in part.

We have agreed to indemnify the underwriters and their controlling persons against certain liabilities, including liabilities under the Securities Act of 1933, as amended (the “Securities Act”), or to contribute to payments the underwriters may be required to make in respect of those liabilities.

The underwriters propose to offer the Notes directly to the public at the relevant public offering price set forth on the cover page of this prospectus supplement and may offer the Notes to dealers at the relevant public offering price less a concession not to exceed  % of the principal amount of the 2027 Notes,  % of the principal amount of the 2029 Notes, % of the principal amount of the 2032 Notes,  % of the principal amount of the 2035 Notes and % of the principal amount of the 2055 Notes. The underwriters may allow, and dealers may re-allow, a concession not to exceed % of the principal amount of the 2027 Notes,  % of the principal amount of the 2029 Notes, % of the principal amount of the 2032 Notes,  % of the principal amount of the 2035 Notes and % of the principal amount of the 2055 Notes on sales to other dealers. After the initial offering of the Notes to the public, the representatives may change the relevant public offering price and concession.

The following table shows the underwriting discount that we are to pay to the underwriters in connection with this offering (expressed as a percentage of the principal amount of the Notes).

	Paid by the Company
Per 2027 Note			%
Per 2029 Note			%
Per 2032 Note			%
Per 2035 Note			%
Per 2055 Note			%

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We estimate that our total expenses (excluding the underwriting discount) for this offering will be approximately $     .

In connection with the offering, the underwriters, may purchase and sell Notes in the open market. These transactions may include over-allotment, syndicate covering transactions and stabilizing transactions. Over-allotment involves syndicate sales of Notes in excess of the principal amounts of the Notes to be purchased by the underwriters in the offering, which creates syndicate short positions. Syndicate covering transactions involve purchases of the Notes in the open market after the distribution has been completed in order to cover syndicate short positions. Stabilizing transactions consist of certain bids for or purchases of Notes made for the purpose of preventing or retarding a decline in the market prices of the Notes while the offering is in progress.

Any of these activities may have the effect of preventing or retarding a decline in the market prices of the Notes. They may also cause the prices of the Notes to be higher than the price that would otherwise exist in the open market in the absence of these transactions. The underwriters may conduct these transactions in the over-the-counter market or otherwise. If the underwriters commence any of these transactions, they may discontinue them at any time.

The Notes are a new issue of securities with no established trading market. We do not intend to apply for listing of the Notes on any national securities exchange or for inclusion of the Notes on any automated dealer quotation system. We have been advised by the underwriters that they presently intend to make a market in the Notes after completion of the offering. However, they are under no obligation to do so and may discontinue any market-making activities at any time without any notice. We cannot assure the liquidity of the trading market for the Notes or that an active public market for the Notes will develop. If an active public trading market for the Notes does not develop, the market price and liquidity of the Notes may be adversely affected. If the Notes are traded, they may trade at a discount from their initial offering price, depending on prevailing interest rates, the market for similar securities, our operating performance and financial condition, general economic conditions and other factors.

We have agreed that we will not, for a period commencing on the date of this prospectus supplement and ending upon delivery of the Notes, without first obtaining the prior written consent of the representatives (which consent may be withheld at the representatives’ discretion), (i) directly or indirectly, offer, pledge, sell, contract to sell, sell any option or contract to purchase, purchase any option or contract to sell, grant any option, right or warrant for the sale of, or lend or otherwise transfer or dispose of, the Notes or any securities that are substantially similar to the Notes, whether owned as of the date of this prospectus supplement or hereafter acquired or with respect to which such person has or hereafter acquires the power of disposition, or file, or cause to be filed, any registration statement under the 1933 Act with respect to any of the foregoing or (ii) enter into any swap or any other agreement or any transaction that transfers, in whole or in part, directly or indirectly, the economic consequence of ownership of the Notes or such other securities, whether any such transaction, swap or other agreement described in clause (i) or (ii) above is to be settled by delivery of any Notes or such other securities, in cash or otherwise.

The underwriters and their respective affiliates are full service financial institutions engaged in various activities, which may include securities trading, commercial and investment banking, financial advisory, investment management, investment research, principal investment, hedging, financing and brokerage activities. The underwriters and their affiliates have performed commercial banking, investment banking and advisory services for us from time to time for which they have received customary fees and expenses. The underwriters or their affiliates may, from time to time, engage in transactions with and perform services for us in the ordinary course of their business. Certain of the underwriters in this Notes offering are also acting as underwriters in the concurrent Common Stock Offering. Additionally, in connection with the Transaction, BofA Securities, Inc. is providing certain financial advisory services to the Company, and Morgan Stanley & Co. LLC is providing certain financial advisory services to the Acquired Entity (or one of its affiliates).

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In the ordinary course of their various business activities, the underwriters and their respective affiliates may make or hold a broad array of investments and actively trade debt and equity securities (or related derivative securities) and financial instruments (including bank loans) for their own account and for the accounts of their customers, and such investment and securities activities may involve securities and/or instruments of the Company. The underwriters and their respective affiliates may also make investment recommendations and/or publish or express independent research views in respect of such securities or instruments and may at any time hold, or recommend to clients that they acquire, long and/or short positions in such securities and instruments. If any of the underwriters or their affiliates have a lending relationship with us, certain of those underwriters or their affiliates routinely hedge, and certain other of those underwriters or their affiliates may hedge, their credit exposure to us consistent with their customary risk management policies. Typically, these underwriters and their affiliates would hedge such exposure by entering into transactions which consist of either the purchase of credit default swaps or the creation of short positions in our securities, including potentially the Notes offered hereby. Any such credit default swaps or short positions could adversely affect future trading prices of the Notes offered hereby.

We expect to deliver the Notes against payment for the Notes on the seventh business day following the date of the pricing of the Notes, which we refer to as T+7. Under Rule 15c6-1 of the Exchange Act, trades in the secondary market generally are required to settle in one business day, unless the parties to a trade expressly agree otherwise. Accordingly, investors who wish to trade Notes prior to the business day before settlement will be required, by virtue of the fact that the Notes initially will settle in T+7, to specify alternative settlement arrangements to prevent a failed settlement.

Notice to Prospective Investors in Canada

The Notes may be sold only to purchasers purchasing, or deemed to be purchasing, as principal that are accredited investors, as defined in National Instrument 45-106 Prospectus Exemptions or subsection 73.3(1) of the Securities Act (Ontario), and are permitted clients, as defined in National Instrument 31-103 Registration Requirements, Exemptions and Ongoing Registrant Obligations. Any resale of the Notes must be made in accordance with an exemption from, or in a transaction not subject to, the prospectus requirements of applicable securities laws.

Securities legislation in certain provinces or territories of Canada may provide a purchaser with remedies for rescission or damages if this prospectus supplement and the accompanying prospectus (including any amendment thereto) contain a misrepresentation, provided that the remedies for rescission or damages are exercised by the purchaser within the time limit prescribed by the securities legislation of the purchaser’s province or territory.

The purchaser should refer to any applicable provisions of the securities legislation of the purchaser’s province or territory for particulars of these rights or consult with a legal advisor.

Pursuant to section 3A.3 of National Instrument 33-105 Underwriting Conflicts (NI 33-105), the underwriters are not required to comply with the disclosure requirements of NI 33-105 regarding underwriter conflicts of interest in connection with this offering.

Notice to Prospective Investors in the European Economic Area

This prospectus supplement and the accompanying prospectus have been prepared on the basis that any offer of the Notes in any Member State of the EEA will be made pursuant to an exemption under the Prospectus Regulation from the requirement to publish a prospectus for offers of securities. The expression “Prospectus Regulation” means Regulation (EU) 2017/1129 (as amended or superseded). For the avoidance of doubt, whilst this document is referred to as a ‘prospectus,’ it is not a prospectus for the purposes of the Prospectus Regulation.

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The Notes are not intended to be offered, sold or otherwise made available to and should not be offered, sold or otherwise made available to any retail investor in the EEA. For the purposes of this provision:

(a) the expression “retail investor” means a person who is one (or more) of the following:

(i) a retail client as defined in point (11) of Article 4(1) of Directive 2014/65/EU (as amended, “MiFID II”);

(ii) a customer within the meaning of Directive (EU) 2016/97 (as amended, the “Insurance Distribution Directive”), where that customer would not qualify as a professional client as defined in point (10) of Article 4(1) of MiFID II; or

(iii) not a qualified investor as defined in Article 2(e) of the Prospectus Regulation; and

(b) the expression “offer” includes the communication in any form and by any means, presenting sufficient information on the terms of the offer and the securities to be offered, so as to enable an investor to decide to purchase or subscribe for those securities.

Consequently, no key information document required by Regulation (EU) No 1286/2014 (as amended, the “PRIIPs Regulation”) for offering or selling packaged retail and insurance based investment products or otherwise making them available to retail investors in the EEA has been prepared, and therefore offering or selling the Notes or otherwise making them available to any retail investor in the EEA may be unlawful under the PRIIPs Regulation.

In the EEA, this prospectus supplement and the accompanying prospectus and any other material in relation to the Notes are only being distributed to, and are only directed at, “non-retail investors” (being persons who are not “retail investors” as defined in this section titled “Notice to Prospective Investors in the European Economic Area”) and any investment or investment activity to which this prospectus supplement and the accompanying prospectus relate is available only to, and will be engaged in only with, non-retail investors. This prospectus supplement, the accompanying prospectus and their contents are confidential and should not be distributed, published or reproduced (in whole or in part) or disclosed by any recipients to any other persons in the EEA. Any person in the EEA who is a “retail investor” should not act or rely on this prospectus supplement, the accompanying prospectus or their contents. Each person in the EEA who purchases any of the Notes will be deemed to have represented, warranted, acknowledged and agreed that they are a non-retail investor.

Prohibition of Sales to United Kingdom Retail Investors

This prospectus supplement and the accompanying prospectus have been prepared on the basis that any offer of the Notes in the UK will be made pursuant to an exemption from the requirement to publish a prospectus for offers of securities. For the avoidance of doubt, whilst this document is referred to as a ‘prospectus,’ it is not a prospectus for the purposes of UK law.

The Notes are not intended to be offered, sold or otherwise made available to and should not be offered, sold or otherwise made available to any retail investor in the UK. For the purposes of this provision:

(a) the expression “retail investor” means a person who is one (or more) of the following:

(i) a retail client as defined in point (8) of Article 2 of Regulation (EU) No 2017/565 as it forms part of domestic law by virtue of the European Union (Withdrawal) Act 2018 (as amended, and together with any statutory instruments made in exercise of the powers conferred by such Act, the “EUWA”);

(ii) a customer within the meaning of the provisions of the Financial Services and Markets Act 2000 (as amended, the “FSMA”) and any rules or regulations made under the FSMA to implement Directive (EU) 2016/97, where that customer would not qualify as a professional client as defined in point (8) of Article 2(1) of Regulation (EU) No 600/2014 as it forms part of domestic law by virtue of the EUWA; or

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(iii) not a qualified investor as defined in Article 2 of Regulation (EU) 2017/1129 as it forms part of domestic law by virtue of the EUWA; and

(b) the expression “offer” includes the communication in any form and by any means, presenting sufficient information on the terms of the offer and the securities to be offered, so as to enable an investor to decide to purchase or subscribe for those securities.

Consequently, no key information document required by Regulation (EU) No 1286/2014 as it forms part of domestic law by virtue of the EUWA (the “UK PRIIPs Regulation”) for offering or selling packaged retail and insurance based investment products or otherwise making them available to retail investors in the UK has been prepared, and therefore offering or selling the Notes or otherwise making them available to any retail investor in the UK may be unlawful under the UK PRIIPs Regulation.

In the UK, this prospectus supplement, the accompanying prospectus and any other material in relation to the Notes are only being distributed to, and are only directed at, “non-retail investors” (being persons who are not “retail investors” as defined in this section “Prohibition of Sales to United Kingdom (“UK”) Retail Investors”) who are also: (i) persons having professional experience in matters relating to investments who fall within the definition of “investment professionals” in Article 19(5) of the Financial Services and Markets Act 2000 (Financial Promotion) Order 2005 (as amended, the “Order”); (ii) high net worth bodies corporate, unincorporated associations and partnerships and trustees of high value trusts as described in Article 49(2)(a) to (d) of the Order; or (iii) persons to whom an invitation or inducement to engage in investment activity (within the meaning of section 21 of the FSMA) in connection with the issue or sale of any Notes may otherwise lawfully be communicated or caused to be communicated (all such persons together being referred to as “relevant persons”). This prospectus supplement and the accompanying prospectus and their contents are confidential and should not be distributed, published or reproduced (in whole or in part) or disclosed by any recipients to any other persons in the UK. In the UK, any investment or investment activity to which this prospectus supplement and the accompanying prospectus relate is only available to, and will be engaged in only with, relevant persons. Any person in the UK that is not a relevant person should not act or rely on this prospectus supplement, the accompanying prospectus or their contents. Each person in the UK who purchases any of the Notes will be deemed to have represented, warranted, acknowledged and agreed that they are a relevant person.

In the UK, the Notes may not be offered other than by an underwriter that:

• has only communicated or caused to be communicated and will only communicate or cause to be communicated an invitation or inducement to engage in investment activity (within the meaning of Section 21 of the FSMA) received by it in connection with the issue or sale of the Notes in circumstances in which Section 21(1) of the FSMA is complied with or does not apply; and

• has complied and will comply with all applicable provisions of the FSMA with respect to anything done by it in relation to the Notes in, from or otherwise involving the UK.

References in this section titled “Prohibition of Sales to United Kingdom (“UK”) Retail Investors” to UK legislation include any successor legislation to that legislation.

Notice to Prospective Investors in Hong Kong

The Notes have not been offered or sold and will not be offered or sold in Hong Kong, by means of any document, other than (a) to “professional investors” as defined in the Securities and Futures Ordinance (Cap. 571) of Hong Kong and any rules made under that Ordinance; or (b) in other circumstances which do not result in the document being a “prospectus” as defined in the Companies (Winding Up and Miscellaneous Provisions) Ordinance (Cap. 32) of Hong Kong or which do not constitute an offer to the public within the meaning of that Ordinance. No advertisement, invitation or document relating to the Notes has been or may be issued or has been or may be in the possession of any person for the purposes of issue, whether in Hong Kong or

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elsewhere, which is directed at, or the contents of which are likely to be accessed or read by, the public of Hong Kong (except if permitted to do so under the securities laws of Hong Kong) other than with respect to Notes which are or are intended to be disposed of only to persons outside Hong Kong or only to “professional investors” as defined in the Securities and Futures Ordinance (Cap. 571) of Hong Kong and any rules made under that Ordinance.

Notice to Prospective Investors in Japan

The Notes have not been and will not be registered under the Financial Instruments and Exchange Law of Japan (the “Financial Instruments and Exchange Law”) and each underwriter has agreed that it will not offer or sell any of the Notes, directly or indirectly, in Japan or to, or for the account or benefit of, any resident of Japan (which term as used herein means any person resident in Japan, including any corporation or other entity organized under the laws of Japan), or to, or for the account or benefit of, others for re-offering or resale, directly or indirectly, in Japan or to, or for the account or benefit of, a resident of Japan, except pursuant to an exemption from the registration requirements of, and otherwise in compliance with, the Financial Instruments and Exchange Law and any other applicable laws, regulations and governmental guidelines of Japan.

Notice to Prospective Investors in Singapore

This prospectus supplement and the accompanying prospectus has not been and will not be registered as a prospectus under the Securities and Futures Act, Chapter 289 of Singapore (the “SFA”) by the Monetary Authority of Singapore, and the offer of the Notes in Singapore is made primarily pursuant to the exemptions under Sections 274 and 275 of the SFA. Accordingly, this prospectus supplement, the accompanying prospectus and any other document or material in connection with the offer or sale, or invitation for subscription or purchase, of the Notes may not be circulated or distributed, nor may the Notes be offered or sold, or be made the subject of an invitation for subscription or purchase, whether directly or indirectly, to any person in Singapore other than (i) to an institutional investor as defined in Section 4A of the SFA (an “Institutional Investor”) pursuant to Section 274 of the SFA, (ii) to an accredited investor as defined in Section 4A of the SFA (an “Accredited Investor”) or other relevant person as defined in Section 275(2) of the SFA (a “Relevant Person”) and pursuant to Section 275(1) of the SFA, or to any person pursuant to an offer referred to in Section 275(1A) of the SFA, and in accordance with the conditions specified in Section 275 of the SFA and (where applicable) Regulation 3 of the Securities and Futures (Classes of Investors) Regulations 2018 or (iii) otherwise pursuant to, and in accordance with the conditions of, any other applicable exemption or provision of the SFA.

It is a condition of the offer that where the Notes are subscribed for or acquired pursuant to an offer made in reliance on Section 275 of the SFA by a Relevant Person which is:

(a) a corporation (which is not an Accredited Investor), the sole business of which is to hold investments and the entire share capital of which is owned by one or more individuals, each of whom is an Accredited Investor; or

(b) a trust (where the trustee is not an Accredited Investor), the sole purpose of which is to hold investments and each beneficiary of the trust is an individual who is an Accredited Investor, securities,

or securities-based derivatives contracts (each term as defined in Section 2(1) of the SFA) of that corporation and the beneficiaries’ rights and interest (howsoever described) in that trust shall not be transferred within 6 months after that corporation or that trust has subscribed for or acquired the Notes except:

(1) to an Institutional Investor, an Accredited Investor, a Relevant Person or which arises from an offer referred to in Section 275(1A) of the SFA (in the case of that corporation) or Section 276(4)(i)(B) of the SFA (in the case of that trust);

(2) where no consideration is or will be given for the transfer;

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(3) where the transfer is by operation of law;

(4) as specified in Section 276(7) of the SFA; or

(5) as specified in Regulation 37A of the Securities and Futures (Offers of Investments) (Securities and Securities-based Derivatives Contracts) Regulations 2018.

Singapore Securities and Futures Act Product Classification—Solely for the purposes of its obligations pursuant to Sections 309B(1)(a) and 309B(1)(c) of the SFA, the Company has determined, and hereby notifies all relevant persons (as defined in Section 309A of the SFA) that the Notes are “prescribed capital markets products” (as defined in the Securities and Futures (Capital Markets Products) Regulations 2018) and “Excluded Investment Products” (as defined in MAS Notice SFA 04-N12: Notice on the Sale of Investment Products and MAS Notice FAA-N16: Notice on Recommendations on Investment Products).

Notice to Prospective Investors in Switzerland

This prospectus supplement is not intended to constitute an offer or solicitation to purchase or invest in the Notes. The Notes may not be publicly offered, directly or indirectly, in Switzerland within the meaning of the Swiss Financial Services Act (“FinSA”) and no application has or will be made to admit the Notes to trading on any trading venue (exchange or multilateral trading facility) in Switzerland. Neither this prospectus supplement nor any other offering or marketing material relating to the Notes constitutes a prospectus pursuant to the FinSA, and neither this prospectus supplement nor any other offering or marketing material related to the Notes may be publicly distributed or otherwise made publicly available in Switzerland.

Notice to Prospective Investors in Taiwan

The Notes have not been and will not be registered or filed with, or approved by, the Financial Supervisory Commission of Taiwan, the Republic of China (“Taiwan”) and/or other regulatory authority of Taiwan pursuant to relevant securities laws and regulations and may not be sold, issued or offered within Taiwan through a public offering or in circumstances which could constitute an offer within the meaning of the Securities and Exchange Act of Taiwan or relevant laws and regulations that requires a registration, filing or approval of the Financial Supervisory Commission of Taiwan and/or other regulatory authority of Taiwan. No person or entity in Taiwan has been authorized to offer, sell, distribute or otherwise intermediate the Notes in Taiwan through a public offering or in any offering that requires registration, filing or approval of the Financial Supervisory Commission of Taiwan except pursuant to the applicable laws and regulations of Taiwan and the competent authority’s rulings thereunder.

Notice to Prospective Investors in the Dubai International Financial Centre (the “DIFC”)

This prospectus supplement relates to an Exempt Offer in accordance with the Offered Securities Rules of the Dubai Financial Services Authority (“DFSA”). This prospectus supplement is intended for distribution only to persons of a type specified in the Offered Securities Rules of the DFSA. It must not be delivered to, or relied on by, any other person. The DFSA has no responsibility for reviewing or verifying any documents in connection with Exempt Offers. The DFSA has not approved this prospectus supplement nor taken steps to verify the information set forth herein and has no responsibility for this prospectus supplement. The Notes to which this prospectus supplement relates may be illiquid and/or subject to restrictions on their resale. Prospective purchasers of the Notes offered should conduct their own due diligence on the Notes. If you do not understand the contents of this prospectus supplement you should consult an authorized financial advisor.

In relation to its use in the DIFC, this document is strictly private and confidential and is being distributed to a limited number of investors and must not be provided to any person other than the original recipient, and may not be reproduced or used for any other purpose. The interests in the securities may not be offered or sold directly or indirectly to the public in the DIFC.

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Notice to Prospective Investors in Australia

No placement document, prospectus, product disclosure statement or other disclosure document has been lodged with the Australian Securities and Investments Commission (“ASIC”) or any other governmental agency, in relation to this offering. This prospectus supplement and the accompanying prospectus do not constitute a prospectus, product disclosure statement or other disclosure document under the Corporations Act 2001 (the “Corporations Act”), and do not purport to include the information required for a prospectus, product disclosure statement or other disclosure document under the Corporations Act.

Any offer in Australia of the Notes may only be made to persons (the “Exempt Investors”) who are “sophisticated investors” (within the meaning of section 708(8) of the Corporations Act), “professional investors” (within the meaning of section 708(11) of the Corporations Act) or otherwise pursuant to one or more exemptions contained in section 708 of the Corporations Act so that it is lawful to offer the Notes without disclosure to investors under Chapter 6D of the Corporations Act.

The Notes applied for by Exempt Investors in Australia must not be offered for sale in Australia in the period of 12 months after the date of allotment under the offering, except in circumstances where disclosure to investors under Chapter 6D of the Corporations Act would not be required pursuant to an exemption under section 708 of the Corporations Act or otherwise or where the offer is pursuant to a disclosure document which complies with Chapter 6D of the Corporations Act. Any person acquiring Notes must observe such Australian on-sale restrictions.

This prospectus supplement and the accompanying prospectus contain general information only and do not take account of the investment objectives, financial situation or particular needs of any particular person. They do not contain any securities recommendations or financial product advice. Before making an investment decision, investors need to consider whether the information in this prospectus supplement and the accompanying prospectus is appropriate to their needs, objectives and circumstances, and, if necessary, seek expert advice on those matters.

Notice to Prospective Investors in the United Arab Emirates

The Notes have not been, and are not being, publicly offered, sold, promoted or advertised in the United Arab Emirates (including the Dubai International Financial Centre) other than in compliance with the laws of the United Arab Emirates (and the Dubai International Financial Centre) governing the issue, offering and sale of securities. Further, this prospectus supplement and the accompanying prospectus do not constitute a public offer of securities in the United Arab Emirates (including the Dubai International Financial Centre) and are not intended to be a public offer. This prospectus supplement and the accompanying prospectus have not been approved by or filed with the Central Bank of the United Arab Emirates, the Securities and Commodities Authority or the Dubai Financial Services Authority.

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LEGAL MATTERS

The validity of the Notes offered hereby will be passed upon for us by Gibson, Dunn & Crutcher LLP, New York, New York. Certain legal matters relating to the Notes offered hereby will be passed upon for the underwriters by Cleary Gottlieb Steen & Hamilton LLP, New York, New York.

EXPERTS

The consolidated financial statements and related financial statement schedule of Arthur J. Gallagher & Co. appearing in Arthur J. Gallagher & Co.’s Annual Report (Form 10-K) for the year ended December 31, 2023, and the effectiveness of Arthur J. Gallagher & Co.’s internal control over financial reporting as of December 31, 2023, have been audited by Ernst & Young LLP, independent registered public accounting firm, as set forth in their reports thereon, included therein and incorporated herein by reference. Such consolidated financial statements and related financial statement schedule are incorporated herein by reference in reliance upon such reports given on the authority of such firm as experts in accounting and auditing.

The audited historical financial statements of the Acquired Entity attached as Exhibit 99.2 in Arthur J. Gallagher & Co.’s Current Report on Form 8-K dated December 7, 2024 have been so incorporated in reliance on the report of PricewaterhouseCoopers LLP, independent accountants, given on the authority of said firm as experts in auditing and accounting.

WHERE YOU CAN FIND ADDITIONAL INFORMATION

We are subject to the informational requirements of the Exchange Act and, in accordance with these requirements, we file annual, quarterly and current reports, proxy statements and other information relating to our business, financial condition and other matters with the SEC. We are required to disclose in such reports certain information, as of particular dates, concerning our operating results and financial condition, officers and directors, principal holders of securities, any material interests of such persons in transactions with us and other matters.

Our filings are available to the public through the website maintained by the SEC at http://www.sec.gov. Our filings are also available on our investor relations website at https://investor.ajg.com. You are encouraged to read the materials that we file with the SEC, which disclose important information about us. This information includes any filing we have made with the SEC under Sections 13(a), 13(c), 14 or 15(d) of the Exchange Act. The information on our website or any other website is not incorporated by reference in this prospectus supplement or the accompanying prospectus and should not be considered part of this prospectus supplement or the accompanying prospectus or any other filing we make with the SEC.

INCORPORATION BY REFERENCE

The SEC allows us to “incorporate by reference” into this prospectus supplement and the accompanying prospectus, which means that we can disclose important information to you by referring you to another document that we filed separately with the SEC. The information incorporated by reference is deemed to be part of this prospectus supplement and the accompanying prospectus, except for any information superseded by information contained directly in this prospectus supplement and the accompanying prospectus. These documents contain important information about us and our financial condition, business and results.

We are incorporating by reference into this prospectus supplement the documents listed below and any additional documents that we may file with the SEC pursuant to Sections 13(a), 13(c), 14 or 15(d) of the

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Exchange Act on or after the date we file this prospectus supplement and before the termination of the offering of the securities made under this prospectus supplement. These additional documents include periodic reports, such as Annual Reports on Form 10-K, Quarterly Reports on Form 10-Q and Current Reports on Form 8-K; except we are not incorporating by reference any information, documents or portions of any documents that are not deemed “filed” with the SEC, including any information furnished (but not filed) under Item 2.02 or Item 7.01 of any Current Report on Form 8-K or corresponding information furnished under Item 9.01 of Form 8-K (or included as an exhibit) in any past or future current report on Form 8-K that we may file with the SEC, unless specifically noted below:

• Our Annual Report on Form 10-K for the fiscal year ended December 31, 2023, filed with the SEC on February 9, 2024;

• The portions of our proxy statement for our 2024 annual meeting of stockholders filed with the SEC on March 22, 2024 that are incorporated by reference into our Annual Report on Form 10-K for the fiscal year ended December 31, 2023;

• Our Quarterly Reports on Form 10-Q for the quarterly periods ended March 31, 2024, June  30, 2024, and September 30, 2024, filed with the SEC on May 1, 2024, July 26, 2024 and October 29, 2024, respectively; and

• Our Current Report on Form 8-K filed on February 15, 2024, March  14, 2024, May  8, 2024, July  25, 2024 (Item 5.02 only), and December 9, 2024.

Information in this prospectus supplement supersedes related information in the documents listed above and information in subsequently filed documents supersedes related information in both this prospectus supplement and the incorporated documents.

You may request orally or in writing, and we will provide you with, a copy of these filings, at no cost, by calling us at (630) 773-3800 or by writing to us at the following address:

General Counsel

Arthur J. Gallagher & Co.

2850 Golf Road

Rolling Meadows, Illinois 60008-4050

These filings and reports can also be found on our investor relations website, located at https://investor.ajg.com. Additionally, you may obtain copies of any of these through the SEC’s website at http://www.sec.gov. The information on our website or any other website is not incorporated by reference in this prospectus supplement or the accompanying prospectus and should not be considered part of this prospectus supplement or the accompanying prospectus or any other filing we make with the SEC.

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PROSPECTUS

DEBT SECURITIES

GUARANTEES

COMMON STOCK

PREFERRED STOCK

WARRANTS

DEPOSITARY SHARES

PURCHASE CONTRACTS

UNITS

We may from time to time offer to sell our debt securities, guarantees of debt securities, common stock or preferred stock, either separately or represented by warrants, depositary shares or purchase contracts, as well as units that include any of these securities or securities of other entities. The debt securities may consist of debentures, notes or other types of debt. We may also use this prospectus from time to time to register these securities that may be offered and sold by selling securityholders.

Each time we sell securities pursuant to this prospectus, we will provide a prospectus supplement and attach it to this prospectus. The prospectus supplement will contain more specific information about the terms of that offering. The prospectus supplement may also add, update or change information contained in this prospectus. This prospectus may not be used to offer or sell these securities without a prospectus supplement describing the method and terms of the offering. You should carefully read this prospectus and any accompanying prospectus supplement, together with the information we incorporate by reference, before you make your investment decision.

We may sell these securities on a continuous or delayed basis directly, through agents or underwriters designated from time to time or through a combination of these methods. For additional information on the method of sale, you should refer to the section of this prospectus entitled “Plan of Distribution” on page 10. We reserve the sole right to accept, and together with any agents, dealers and underwriters, reserve the right to reject, in whole or in part, any proposed purchase of these securities. If any agents, dealers or underwriters are involved in the sale of these securities, the applicable prospectus supplement will set forth the names and any applicable commissions or discounts.

Our common stock is traded on the New York Stock Exchange under the symbol “AJG.”

Investing in these securities involves risks. You should carefully read and consider the risks referenced under “Risk Factors” beginning on page 3 of this prospectus for a discussion of the factors you should carefully consider, as well as the other information contained in or incorporated by reference in this prospectus or in any accompanying prospectus supplement, in determining whether to invest in these securities.

Neither the Securities and Exchange Commission nor any state securities commission has approved or disapproved of these securities or passed upon the adequacy or accuracy of this prospectus. Any representation to the contrary is a criminal offense.

The date of this prospectus is February 12, 2024.

TABLE OF CONTENTS

	Page
ABOUT THIS PROSPECTUS		1
ARTHUR J. GALLAGHER & CO.		2
RISK FACTORS		3
CAUTIONARY STATEMENT REGARDING FORWARD-LOOKING STATEMENTS		4
USE OF PROCEEDS		8
SELLING SECURITYHOLDERS		9
DESCRIPTION OF SECURITIES		10
PLAN OF DISTRIBUTION		11
LEGAL MATTERS		12
EXPERTS		13
WHERE YOU CAN FIND MORE INFORMATION		14
INCORPORATION OF CERTAIN INFORMATION BY REFERENCE		15

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ABOUT THIS PROSPECTUS

This prospectus is part of a “shelf” registration statement on Form S-3 that we filed with the Securities and Exchange Commission, or SEC. Under the shelf registration process, we may from time to time, offer and sell the securities described in this prospectus or use this prospectus to register securities that may be offered and sold by selling securityholders from time to time. This prospectus provides a general description of the securities that we may offer and sell and that may be offered and sold by selling securityholders. Each time we offer and sell these securities, we will provide a prospectus supplement containing specific information about the terms of the securities being offered and the manner in which it may be offered. We may add, update or change the information contained in this prospectus by means of one or more prospectus supplements. If there is any inconsistency between the information in this prospectus and the applicable prospectus supplement, you should rely on the information in the prospectus supplement. Before investing in our securities, both this prospectus and any prospectus supplement, together with the additional information described under the headings “Where You Can Find More Information” and “Incorporation of Certain Information by Reference,” should be carefully reviewed.

You should rely only on information contained in or incorporated by reference in this prospectus. We have not authorized anyone to give you any information or make any representation that is different from, or in addition to, that contained in this prospectus or in any of the materials that we have incorporated by reference into this document. If you are in a jurisdiction where offers to sell, or solicitations of offers to purchase, the securities offered by this document are unlawful, or if you are a person to whom it is unlawful to direct these types of activities, then the offer presented in this document does not extend to you. The information contained in this prospectus (including the information contained in any document incorporated by reference in this prospectus) speaks only as of the date of each such document, unless the information specifically indicates that another date applies.

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ARTHUR J. GALLAGHER & CO.

We are engaged in providing insurance brokerage, reinsurance brokerage, consulting services, and third-party property/casualty claims settlement and administration services to entities and individuals in the U.S. and abroad.

We report our results in three segments: brokerage, risk management and corporate. Brokerage and risk management contributed approximately 86% and 14%, respectively, to 2023 revenues. We generate approximately 64% of our revenues for the combined brokerage and risk management segments domestically, with the remaining 36% generated internationally, primarily in the Australia, Canada, New Zealand and the U.K. The corporate segment did not generate revenues in 2023. Our ability to generate tax credits from qualified refined coal pursuant to Internal Revenue Code Section 45 ended in December 2021, and in 2022 we ran off existing chemical supplies as part of the wind down of such investments’ operations, which generated some revenues. Our major sources of operating revenues are commissions, fees and supplemental and contingent revenues from our brokerage operation, and fees including performance-based fees, from risk management operations.

For more information about our business, please refer to the “Business” section in our most recent Annual Report on Form 10-K filed with the SEC and incorporated by reference in this prospectus and the “Management’s Discussion and Analysis of Financial Condition and Results of Operations” sections of our most recent Annual Report on Form 10-K and all subsequent Quarterly Reports on Form 10-Q filed with the SEC and incorporated by reference in this prospectus.

Shares of our common stock are traded on the New York Stock Exchange under the symbol “AJG”. We were reincorporated as a Delaware corporation in 1972. Our executive offices are located at 2850 Golf Road, Rolling Meadows, Illinois 60008-4050, and our telephone number is (630) 773-3800.

Unless the context otherwise requires, the terms “we,” “our,” “Gallagher”, and “us” refer to Arthur J. Gallagher & Co. and/or its subsidiaries, as appropriate. The term “you” refers to a prospective investor.

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RISK FACTORS

Investing in our securities involves risks. Before making an investment decision regarding our securities, in addition to the other information, documents or reports included in or incorporated by reference into this prospectus and any accompanying prospectus supplement or other offering materials, you should carefully consider the specific risks set forth under the caption “Risk Factors” in the applicable prospectus supplement as well as our Annual Report on Form 10-K for the fiscal year ended December 31, 2023, which is incorporated by reference into this prospectus and any prospectus supplement, in their entirety, as the same may be amended, supplemented or superseded from time to time by our filings under the Exchange Act of 1934, as amended (the “Exchange Act”). For more information, see the section entitled “Where You Can Find More Information.” If any one or more of the risks set forth in the applicable prospectus supplement or documents incorporated by reference into this prospectus occur, they could materially and adversely affect our business, financial condition or results of operations. Consequently, the trading price of our securities could decline, and you may lose all or part of your investment.

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CAUTIONARY STATEMENT REGARDING FORWARD-LOOKING STATEMENTS

This prospectus, the accompanying prospectus supplement and the documents they incorporate by reference, contain certain statements related to future results, or state our intentions, beliefs and expectations or predictions for the future, which are forward-looking statements as that term is defined in the Private Securities Litigation Reform Act of 1995. Forward-looking statements relate to expectations or forecasts of future events. Such statements use words such as “anticipate,” “believe,” “estimate,” “expect,” “contemplate,” “forecast,” “project,” “intend,” “plan,” “potential,” and other similar terms, and future or conditional tense verbs like “could,” “may,” “might,” “see,” “should,” “will” and “would.” You can also identify forward-looking statements by the fact that they do not relate strictly to historical or current facts. For example, we may use forward-looking statements when addressing topics such as: the impact of general economic conditions, including significant inflation, interest rates and market uncertainty; the effects of geopolitical volatility, including repercussions from the wars in Ukraine and the Middle East; market and industry conditions, including competitive and pricing trends; acquisition strategy including the expected size of our acquisition program; the expected impact of acquisitions and dispositions and integrating recent acquisitions, including comments regarding the expected benefits of our acquisition of the Willis Towers Watson plc treaty reinsurance brokerage operations (which we refer to as Willis Re), BCHR Holdings, L.P., and its subsidiaries, dba Buck (which we refer to as Buck), Cadence Insurance, Inc. (which we refer to as Cadence Insurance), Eastern Insurance Group, LLC (which we refer to as Eastern Insurance), My Plan Manager Group Pty Ltd (which we refer to as My Plan Manager), and other acquisitions larger than our typical tuck-in acquisitions and the expected duration and costs of integrating such large acquisitions; the development and performance of our services and products; changes in the composition or level of our revenues or earnings; our cost structure and the size and outcome of cost-saving or restructuring initiatives; future capital expenditures; future debt levels and anticipated actions to be taken in connection with maturing debt; future debt to earnings ratios; the outcome of contingencies; dividend policy; pension obligations; cash flow and liquidity; capital structure and financial losses; future actions by regulators; the outcome of existing regulatory actions, audits, reviews or litigation; the impact of changes in accounting rules; financial markets; interest rates; foreign exchange rates; matters relating to our operations; income taxes; expectations regarding our investments; human capital management, including diversity and inclusion initiatives, and environmental, social and governance matters, including climate-resilience and climate-advising products and services and carbon emissions. These forward-looking statements are subject to certain risks and uncertainties that could cause actual results to differ materially from either historical or anticipated results depending on a variety of factors.

Potential factors that could impact results include:

• Global economic and geopolitical events, such as high inflation and related monetary policy responses including increased interest rates; a recession or economic downturn; failures of financial institutions and other counterparties or a potential United States (U.S.) government shutdown or gridlock over increasing the U.S. debt ceiling; political violence, and instability, including geo-economic fragmentation;

• Economic conditions that result in financial difficulties for underwriting enterprises or lead to reduced risk-taking capital capacity, for example, as a result of large payouts related to extreme weather events, or to the failure of such enterprises, including the increased risk of errors and omissions (which we refer to as E&O) claims against us;

• Risks that could negatively affect the success of our acquisition strategy, including the impact of current economic uncertainty on our ability to source, review and price acquisitions, continuing consolidation in our industry and interest in acquiring insurance brokers on the part of private equity firms and newly public insurance brokers, which makes it more difficult to identify targets and in some cases makes them more expensive, inaccurate assumptions and failure to realize expected benefits; the risk that we may not receive timely regulatory approval of pending transactions, closing risks; execution risks, integration risks, poor cultural fit, the risk of post-acquisition deterioration leading to

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intangible asset impairment charges, and the risk we could incur or assume unanticipated liabilities such as cybersecurity issues or those relating to violations of anti-corruption and sanctions laws;

• Risks related to Willis Re, Buck, Cadence Insurance, Eastern Insurance, My Plan Manager and other acquisitions larger than our usual tuck-in acquisitions, including risks related to our ability to successfully integrate operations, the possibility that our assumptions may be inaccurate resulting in unforeseen obligations or liabilities and failure to realize the expected benefits of these acquisitions;

• Damage to our reputation, including as a result of environmental, social and governance (which we refer to as ESG) matters and the potential for the Internet and social media to magnify the effects of such reputational issues;

• Failure to meet our sustainability and ESG-related aspirations, goals and initiatives or to comply with increasingly complex climate-related regulations, including increased risks related to “greenwashing”;

• Emerging risks relating to the use of artificial intelligence (which we refer to as AI) in our business operations, including regulatory, data privacy and cybersecurity risks;

• Failure to apply technology, data analytics and AI effectively in driving value for our clients through technology-based solutions, or failure to gain internal efficiencies and effective internal controls through the application of technology and related tools;

• Risks associated with the use of AI in our business operations, including regulatory, data privacy, cybersecurity, E&O and competition risks;

• Failure to attract and retain experienced and qualified talent, including our senior management team, or adequately plan and execute for the succession of such leaders; increased costs resulting from increased compensation and benefits packages as a result of a tighter labor market, and negative effects from restrictions on non-competes at the state and federal level;

• Substantial increase in remote work among our employees, which may affect our corporate culture, productivity, collaboration and effective communication, increase cybersecurity or data breaches risks, heighten vulnerability to solicitations by competing firms and impact our ability to recruit and retain employees that prefer fully remote or fully-in-person work environments;

• A disaster or other significant disruption to business continuity for our own operations or those of third-parties on which we rely, including cybersecurity incidents; natural disasters; political violence and unrest in the U.S. or elsewhere around the world; for example, our substantial operations in India could be negatively impacted as a result of the dispute between India and Pakistan involving the Kashmir region, rising tensions between India and China, or incidents of terrorism in India, civil unrest or other reasons;

• Sustained increases in the cost of employee benefits and compensation expense;

• Risks arising from our international operations and changes in international conditions, including the risks posed by political and economic uncertainty in certain countries (including repercussions from the wars in Ukraine and the Middle East), risks related to maintaining regulatory and legal compliance across multiple jurisdictions (such as those relating to violations of anti-corruption, sanctions, protectionism, privacy laws and increasingly complex regulatory requirements related to climate change and sustainability issues), as well as, risks related to tariffs, trade wars, or climate change and other long-term environmental, social and governance matters and global health risks;

• Risks related to changes in U.S. or foreign tax laws, including a U.S. or foreign tax rate change, potential changes in guidance related to the U.S. Inflation Reduction Act, the Organisation for Economic Co-operation and Development’s (OECD) global minimum corporate tax regime, and other local policy changes;

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• Competitive pressures, including as a result of innovation, in each of our businesses;

• Volatility or declines in premiums or other adverse trends in the insurance industry;

• The higher level of variability inherent in contingent and supplemental revenues versus standard commission revenues;

• Risks particular to our benefit consulting operations, including risks related to the acquisition of Buck;

• Risks particular to our third-party claims administrations operations, including risks related to the availability of RISX-FACS^®, our proprietary risk management information system, wage inflation, staffing shortages, any slowing of the trend toward outsourcing claims administration, and the concentration of large amounts of revenue with certain clients;

• Climate risks, including the risk of a systemic economic crisis and disruptions to our business caused by the transition to a low-carbon economy;

• Cyber-attacks or other cybersecurity incidents such as the ransomware incident we publicly disclosed in September 2020 and the heightened risk of such attacks as a result of the wars in Ukraine and the Middle East, improper disclosure of confidential, personal or proprietary data and changes to laws and regulations governing cybersecurity and data privacy;

• Unfavorable determinations related to contingencies and legal proceedings;

• Violations or alleged violations of the U.S. Foreign Corrupt Practices Act, the United Kingdom (U.K.) Bribery Act 2010 or other anti-corruption laws and the Foreign Account Tax Compliance provisions of the Hiring Incentives to Restore Employment Act, and the outcome of any existing or future investigation, review, regulatory action or litigation;

• Failure to comply with regulatory requirements, including those related to governance and control requirements in particular jurisdictions, international sanctions, including new sanctions laws as a result of the wars in Ukraine and the Middle East; laws relating to the disclosure of ESG-related matters; laws relating to the use of AI, or a change in regulations or enforcement policies that adversely affects our operations (for example, relating to insurance broker compensation methods or restrictions on non-competes);

• Changes to our financial presentation from new accounting estimates and assumptions;

• Intellectual property risks;

• Risks related to our legacy clean energy investments, including intellectual property claims, environmental and product liability claims, environmental compliance costs and the risk of disallowance by the Internal Revenue Service of previously claimed tax credits;

• The risk that our outstanding debt adversely affects our financial flexibility and restrictions and limitations in the agreements and instruments governing our debt;

• The risk of credit rating downgrades;

• The risk we may not be able to receive dividends or other distributions from subsidiaries, including the effects of significant changes in foreign exchange rates;

• The risk of share ownership dilution when we issue common stock; and

• Volatility of the price of our common stock.

Forward-looking statements are not guarantees of future performance. They involve risks, uncertainties and assumptions, including the risk factors referred to above. Our future performance and actual results or outcomes may differ materially from those expressed in forward-looking statements. Accordingly, you should not place

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undue reliance on forward-looking statements, which speak only as of, and are based on information available to us on, the date of the applicable document. Many of the factors that will determine these results are beyond our ability to control or predict. All subsequent written and oral forward-looking statements attributable to us or any person acting on our behalf are expressly qualified in their entirety by the cautionary statements contained or referred to in this section. Forward-looking statements speak only as of the date that they are made, and we do not undertake any obligation to update any such statements or release publicly any revisions to these forward-looking statements to reflect events or circumstances after the date of this prospectus or to reflect new information, future or unexpected events or otherwise, except as required by applicable law or regulation. In addition, historical, current and forward-looking sustainability-related or ESG-related statements may be based on standards for measuring progress that are still developing, internal controls and processes that continue to evolve, and assumptions that are subject to change in the future.

A detailed discussion of the factors that could cause actual results to differ materially from our published expectations is contained under the heading “Risk Factors” in our filings with the SEC, including our Annual Report on Form 10-K for the fiscal year ended December 31, 2023, and any reports we file with the SEC in the future, which are incorporated by reference into this prospectus.

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USE OF PROCEEDS

Unless otherwise specified in a prospectus supplement accompanying this prospectus, the net proceeds from the sale of the securities to which this prospectus relates will be used for general corporate purposes. Net proceeds may be temporarily invested prior to use. We cannot predict whether the net proceeds, if invested, will yield a favorable return. Our management will have broad discretion in the application of the net proceeds we receive from the sale of the securities offered hereby, and you will be relying on the judgment of our management regarding the application of the net proceeds. We will not receive any proceeds from the sale of securities offered for sale in connection with this prospectus by selling securityholders. The selling securityholders will receive all of the net proceeds from those sales.

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SELLING SECURITYHOLDERS

Information about selling securityholders, where applicable, will be set forth in a prospectus supplement, in a post-effective amendment, or in filings we make with the SEC under the Exchange Act, which are incorporated by reference herein.

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DESCRIPTION OF SECURITIES

We will set forth in the applicable prospectus supplement a description of the debt securities, guarantees, common stock, preferred stock, warrants, depositary shares, purchase contracts, or units that may be offered under this prospectus.

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PLAN OF DISTRIBUTION

We, or any selling securityholders, may offer and sell these securities to or through one or more underwriters, dealers and agents, or directly to purchasers, or a combination thereof, on a continuous or delayed basis. We will provide the specific plan of distribution for any securities to be offered in the applicable prospectus supplement.

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LEGAL MATTERS

Gibson, Dunn & Crutcher LLP will pass upon the validity of the securities being offered by this prospectus. Any underwriters, dealers or agents will be represented by Cleary Gottlieb Steen & Hamilton LLP, New York, New York or by other legal counsel named in the applicable prospectus supplement.

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EXPERTS

The consolidated financial statements and related financial statement schedule of Arthur J. Gallagher & Co. appearing in Arthur J. Gallagher & Co.’s Annual Report (Form 10-K) for the year ended December 31, 2023, and the effectiveness of Arthur J. Gallagher & Co.’s internal control over financial reporting as of December 31, 2023, have been audited by Ernst & Young LLP, independent registered public accounting firm, as set forth in their reports thereon included therein, and incorporated herein by reference. Such consolidated financial statements and related financial statement schedule are incorporated herein by reference in reliance upon such reports given on the authority of such firm as experts in accounting and auditing.

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WHERE YOU CAN FIND MORE INFORMATION

We file annual, quarterly and current reports, proxy statements and other information with the SEC under the Exchange Act. You may access and read our SEC filings, including the complete registration statement of which this prospectus is a part and all of the exhibits to it, through commercial document retrieval services, which are available to the public, and also on the SEC’s website located at http://www.sec.gov. This site contains reports and other information that we file electronically with the SEC.

We have filed a registration statement, of which this prospectus is a part, and related exhibits with the SEC under the Securities Act. This prospectus, filed as part of the registration statement, does not contain all of the information set forth in the registration statement and its exhibits and schedules, portions of which have been omitted as permitted by the rules and regulations of the SEC. For further information about us and our securities, we refer you to the registration statement and its exhibits and schedules.

Statements in this prospectus about the contents of any contract, agreement or other documents are not necessarily complete and, in each instance, we refer you to the copy of such contract, agreement or document filed as an exhibit to the registration statement, with each such statement being qualified in all respects by reference to the document to which it refers.

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INCORPORATION OF CERTAIN INFORMATION BY REFERENCE

We incorporate information into this prospectus by reference, which means that we can disclose important information to you by referring you to those documents, which have been separately filed with the SEC. The information incorporated by reference is considered to be part of this prospectus, and information that we file later with the SEC will automatically update and supersede this information. We are incorporating by reference our filings listed below and any additional documents that we may file with the SEC pursuant to Section 13(a), 13(c), 14 or 15(d) of the Exchange Act on or after the date of this prospectus and before the termination of the offering of the securities made under this prospectus; except we are not incorporating by reference any information, documents or portions of any documents that are not deemed “filed” with the SEC, including any information furnished under Item 2.02 or Item 7.01 of any Current Report on Form 8-K or corresponding information furnished under Item 9.01 of Form 8-K (or included as an exhibit) in any past or future current report on Form 8-K that we may file with the SEC, unless specifically noted below:

• Our Annual Report on Form 10-K for the fiscal year ended December 31, 2023, filed with the SEC on February 9, 2024 (including the portions of our proxy statement for our 2024 annual meeting of stockholders incorporated by reference therein);

• The portions of our proxy statement for our 2023 annual meeting of stockholders filed with the SEC on March  27, 2023 that are incorporated by reference into our Annual Report on Form 10-K for the fiscal year ended December 31, 2022; and

• The description of our common stock contained in our Registration Statement on Form 8-A (registration no. 0-13480), filed with the SEC on November  2, 1987, as updated by the description of our common stock contained in Exhibit 4.1 to our Annual Report on Form 10-K for the fiscal year ended December 31, 2023, and all amendments or reports filed for the purpose of updating such descriptions.

Information in this prospectus supersedes related information in the documents listed above and information in subsequently filed documents supersedes related information in both this prospectus and the incorporated documents.

You may request orally or in writing, and we will provide you with, a copy of these filings, at no cost, by calling us at (630) 773-3800 or by writing to us at the following address:

General Counsel

Arthur J. Gallagher & Co.

2850 Golf Road

Rolling Meadows, Illinois 60008-4050

These filings and reports can also be found on our investor relations website, located at https://investor.ajg.com. Additionally, you may obtain copies of any of these through the SEC’s website: http://www.sec.gov.

The information contained on our website does not constitute a part of this prospectus.

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$    

Arthur J. Gallagher & Co.

$     % Senior Notes due 2027

$     % Senior Notes due 2029

$     % Senior Notes due 2032

$     % Senior Notes due 2035

$     % Senior Notes due 2055

Preliminary Prospectus Supplement

Joint Book-Running Managers

BofA Securities Morgan Stanley

    , 2024