Summary of Significant Accounting Policies (Policies)	6 Months Ended
Mar. 31, 2021
Accounting Policies [Abstract]
Interim Financial Statements	Interim Financial Statements The accompanying unaudited consolidated financial statements have been prepared in accordance with United States generally accepted accounting principles (“U.S. GAAP”) for interim financial information and with the instructions to Form 10-Q and Article 10 of Regulation S-X. Accordingly, they do not include all the information and notes required by U.S. GAAP for complete financial statements. In the opinion of management, all adjustments (consisting of normal recurring accruals) considered necessary for a fair presentation have been included. Operating results for the three and six months ended March 31, 2021 are not necessarily indicative of the results that may be expected for the fiscal year ending September 30, 2021. The consolidated balance sheet at September 30, 2020 has been derived from the audited consolidated financial statements at that date but does not include all the information and notes required by U.S. GAAP for complete financial statements. For further information, refer to the consolidated financial statements and notes thereto included in our Annual Report on Form 10-K for the fiscal year ended September 30, 2020 (File No. 001-32502).
Basis of Consolidation	Basis of Consolidation The accompanying financial statements present the consolidated accounts of all entities in which the Company has a controlling voting interest and/or variable interest required to be consolidated in accordance with U.S. GAAP. All intercompany balances and transactions have been eliminated. Financial Accounting Standards Board (“FASB”) Accounting Standards Codification (“ASC”) Topic 810, Consolidation (“ASC 810”) requires the Company first evaluate its investments to determine if any investments qualify as a variable interest entity (“VIE”). A VIE is consolidated if the Company is deemed to be the primary beneficiary of the VIE, which is the party involved with the VIE that has both (i) the power to control the most significant activities of the VIE and (ii) either the obligation to absorb losses or the right to receive benefits that could potentially be significant to the VIE. If an entity is not deemed to be a VIE, the Company consolidates the entity if the Company has a controlling voting interest. The Company maintains a 52-53 week fiscal year ending on the last Friday in each reporting period. As such, all references to March 31, 2021 and March 31, 2020 relate to the periods ended March 26, 2021 and March 27, 2020, respectively. For convenience purposes, the Company continues to date its second-quarter financial statements as of March 31. The fiscal year ended September 30, 2020 ended on September 25, 2020.
Common Stock	Common Stock On February 28, 2020, the Company amended its certificate of incorporation to increase its authorized capital stock to 2,100,000,000 shares, consisting of 1,000,000,000 shares of Class A Common Stock, 1,000,000,000 shares of Class B Common Stock, and 100,000,000 shares of preferred stock, par value $1.00 per share. In addition, the February 28, 2020 amendment to the Company’s certificate of incorporation also gave effect to the reclassification and 477,242.614671815-for-1 stock split of the Company’s existing common stock outstanding into 510,000,000 shares of Class B Common Stock. This stock split has been retrospectively presented throughout the interim financial statements. Upon completion of the IPO and the exercise in full of the underwriters’ option to purchase additional shares, 88,550,000 shares of Class A Common Stock, 421,450,000 shares of Class B Common Stock and no shares of preferred stock were outstanding. In connection with the IPO, the Company’s board of directors and stockholders approved the Warner Music Group Corp. 2020 Omnibus Incentive Plan, or the “Omnibus Incentive Plan.” The aggregate number of shares of common stock available for issuance under the Omnibus Incentive Plan is 31,169,099 shares of Class A Common Stock over the 10-year period from the date of adoption, including up to 1,000,000 shares of our Class A Common Stock in connection with the IPO. Since the IPO, a total of 61,423 shares of restricted stock has been issued under the Omnibus Incentive Plan to the Company’s directors, which includes 30,509 and 33,062 shares issued during the three and six months ended March 31, 2021, respectively. Refer to “Stock-Based Compensation” below regarding additional shares issued under our Omnibus Incentive Plan. In December 2020, all of the outstanding equity interests held by certain participants in the Second Amended and Restated Warner Music Group Corp. Senior Management Free Cash Flow Plan (the “Plan”) were settled or redeemed in accordance with the terms of the Plan. The Class A and Class B equity units held by certain participants in WMG Management Holdings, LLC (“Management LLC”) were redeemed in exchange for 18,265,183 shares of Class B Common Stock. These shares of Class B Common Stock converted to shares of Class A Common Stock upon exchange. The Company also issued a total of 4,321,259 additional shares of Class A Common Stock to settle the participants’ remaining deferred equity units previously issued under the Plan. In March 2021, the Compensation Committee of the Board of Directors of the Company approved an amendment to the Plan that allowed certain remaining Plan participants to redeem a portion of their vested Class B equity units of Management LLC. These Class B equity units were redeemed in exchange for a total of 968,920 shares of Class B Common Stock, which shares of Class B Common Stock converted to shares of Class A Common Stock upon the exchange. In February 2021, Access converted 4,754,626 shares of Class B Common Stock to the same number of shares of Class A Common Stock, which it subsequently sold through open market sales, which is reflected as an exchange of Class B Common Stock for Class A Common Stock in the consolidated statements of equity for the three and six months ended March 31, 2021.
Earnings per Share	Earnings per Share The consolidated statements of operations present basic and diluted earnings per share (“EPS”). Prior to the completion of the IPO, basic and diluted earnings per share were computed by dividing net income available to common stockholders by the weighted average number of outstanding common shares less shares issued for the exercise of the deferred equity units since these units were mandatorily redeemable in cash. As such, the deferred equity units were excluded from the denominator of the basic and diluted EPS calculation prior to the IPO completion. Subsequent to the completion of the IPO, the Company utilizes the two-class method to report earnings per share. The two-class method is an earnings allocation formula that determines earnings per share for each class of common stock according to dividends declared and participation rights in undistributed earnings. Undistributed earnings allocated to participating securities are subtracted from net income in determining net income attributable to common stockholders.
Stock-Based Compensation	Stock-Based Compensation The Company accounts for stock-based payments as required by ASC 718, Compensation—Stock Compensation (“ASC 718”). Under the recognition provision of ASC 718, the Company’s liability classified stock-based compensation costs are measured each reporting date until settlement. In February 2020, the Company filed a Form S-1 registration statement with the SEC in connection with the IPO, which required a change in accounting policy during the three months ended March 31, 2020 from the intrinsic value method to fair value method in determining the basis of measurement of its stock-based compensation liability. Upon completion of the IPO in June 2020, the Plan was amended to remove the cash-settlement feature on all future redemptions. As a result, all awards previously issued under the Plan required settlement in equity. The participants in such plan were also allowed to sell a pro rata portion, consistent with Access’s percentage reduction in shares of Class B Common Stock as a result of the IPO, of their vested profits interests and acquired units of Management LLC, in the IPO through a “tag-along right.” Under the provision of ASC 718, the Company determined the Plan was modified as of June 3, 2020, and as such, converted the awards from liability-classified to equity-classified. Prior to conversion, the Company performed a final measurement of its stock-based compensation liability under the fair value method. Subsequent to the amendment, the awards issued under the Plan will no longer be adjusted for changes in the value of the Company’s common stock. The Company will continue to incur non-cash stock-based compensation expense for awards that were unvested as of the modification date of the Plan and awards issued under the Omnibus Incentive Plan. During the three and six months ended March 31, 2021, the Company granted restricted stock units (“RSUs”) under the Omnibus Incentive Plan to eligible employees and executives. The Company recognized approximately $15 million and $21 million of non-cash stock-based compensation expense for the three and six months ended March 31, 2021, respectively, of which $11 million and $17 million was recorded to additional paid-in capital, and a remaining $4 million has been classified as a share-based compensation liability as of March 31, 2021. The share-based liability represents executive awards that have not yet been granted under the Omnibus Incentive Plan, where a total value is known and settlement will occur in a variable number of RSUs.
Income Taxes	Income Taxes The Company uses the estimated annual effective tax rate method in computing its interim tax provision. Certain items, including those deemed to be unusual and infrequent are excluded from the estimated annual effective tax rate. In such cases, the actual tax expense or benefit is reported in the same period as the related item. Certain tax effects are also not reflected in the estimated annual effective tax rate, primarily certain changes in the realizability of deferred tax assets and uncertain tax positions.
New Accounting Pronouncements	New Accounting Pronouncements Recently Adopted Accounting Pronouncements In June 2016, the FASB issued ASU 2016-13, Financial Instruments—Credit Losses: Measurement of Credit Losses on Financial Instruments (“ASU 2016-13”). ASU 2016-13 requires that expected credit losses relating to financial assets measured on an amortized cost basis and available-for-sale debt securities be recorded through an allowance for credit losses. ASU 2016-13 limits the amount of credit losses to be recognized for available-for-sale debt securities to the amount by which carrying value exceeds fair value and also requires the reversal of previously recognized credit losses if fair value increases. The Company adopted ASU 2016-13 in the first quarter of fiscal 2021 and this adoption did not have a material impact on the Company’s consolidated financial statements. Accounting Pronouncements Not Yet Adopted In December 2019, the FASB issued ASU 2019-12, Simplifying the Accounting for Income Taxes (“ASU 2019-12”). This ASU eliminates certain exceptions to the general principles in ASC 740, Income Taxes. Specifically, it eliminates the exception to (1) the incremental approach for intraperiod tax allocation when there is a loss from continuing operations, and income or a gain from other items; (2) the requirement to recognize a deferred tax liability for equity method investments when a foreign subsidiary becomes an equity method investment; (3) the ability not to recognize a deferred tax liability for a foreign subsidiary when a foreign equity method investment becomes a subsidiary; and (4) the general methodology for calculating income taxes in an interim period when a year-to-date loss exceeds the anticipated loss for the year. ASU 2019-12 also simplifies U.S. GAAP by making other changes. ASU 2019-12 will be effective for the annual periods beginning after December 15, 2021, and for interim periods beginning after December 15, 2022. Earlier adoption is permitted. The Company is evaluating the impact of the adoption of this standard on its consolidated financial statements.

Summary of Significant Accounting Policies (Policies)

6 Months Ended

Mar. 31, 2021

The accompanying unaudited consolidated financial statements have been prepared in accordance with United States generally accepted accounting principles (“U.S. GAAP”) for interim financial information and with the instructions to Form 10-Q and Article 10 of Regulation S-X. Accordingly, they do not include all the information and notes required by U.S. GAAP for complete financial statements. In the opinion of management, all adjustments (consisting of normal recurring accruals) considered necessary for a fair presentation have been included. Operating results for the three and six months ended March 31, 2021 are not necessarily indicative of the results that may be expected for the fiscal year ending September 30, 2021.

The consolidated balance sheet at September 30, 2020 has been derived from the audited consolidated financial statements at that date but does not include all the information and notes required by U.S. GAAP for complete financial statements.

For further information, refer to the consolidated financial statements and notes thereto included in our Annual Report on Form 10-K for the fiscal year ended September 30, 2020 (File No. 001-32502).

Basis of Consolidation

The accompanying financial statements present the consolidated accounts of all entities in which the Company has a controlling voting interest and/or variable interest required to be consolidated in accordance with U.S. GAAP. All intercompany balances and transactions have been eliminated.

Financial Accounting Standards Board (“FASB”) Accounting Standards Codification (“ASC”) Topic 810, Consolidation (“ASC 810”) requires the Company first evaluate its investments to determine if any investments qualify as a variable interest entity (“VIE”). A VIE is consolidated if the Company is deemed to be the primary beneficiary of the VIE, which is the party involved with the VIE that has both (i) the power to control the most significant activities of the VIE and (ii) either the obligation to absorb losses or the right to receive benefits that could potentially be significant to the VIE. If an entity is not deemed to be a VIE, the Company consolidates the entity if the Company has a controlling voting interest.

The Company maintains a 52-53 week fiscal year ending on the last Friday in each reporting period. As such, all references to March 31, 2021 and March 31, 2020 relate to the periods ended March 26, 2021 and March 27, 2020, respectively. For convenience purposes, the Company continues to date its second-quarter financial statements as of March 31. The fiscal year ended September 30, 2020 ended on September 25, 2020.

Common Stock

On February 28, 2020, the Company amended its certificate of incorporation to increase its authorized capital stock to 2,100,000,000 shares, consisting of 1,000,000,000 shares of Class A Common Stock, 1,000,000,000 shares of Class B Common Stock, and 100,000,000 shares of preferred stock, par value $1.00 per share. In addition, the February 28, 2020 amendment to the Company’s certificate of incorporation also gave effect to the reclassification and 477,242.614671815-for-1 stock split of the Company’s existing common stock outstanding into 510,000,000 shares of Class B Common Stock. This stock split has been retrospectively presented throughout the interim financial statements. Upon completion of the IPO and the exercise in full of the underwriters’ option to purchase additional shares, 88,550,000 shares of Class A Common Stock, 421,450,000 shares of Class B Common Stock and no shares of preferred stock were outstanding.

In connection with the IPO, the Company’s board of directors and stockholders approved the Warner Music Group Corp. 2020 Omnibus Incentive Plan, or the “Omnibus Incentive Plan.” The aggregate number of shares of common stock available for issuance under the Omnibus Incentive Plan is 31,169,099 shares of Class A Common Stock over the 10-year period from the date of adoption, including up to 1,000,000 shares of our Class A Common Stock in connection with the IPO. Since the IPO, a total of 61,423 shares of restricted stock has been issued under the Omnibus Incentive Plan to the Company’s directors, which includes 30,509 and 33,062 shares issued during the three and six months ended March 31, 2021, respectively. Refer to “Stock-Based Compensation” below regarding additional shares issued under our Omnibus Incentive Plan.

In December 2020, all of the outstanding equity interests held by certain participants in the Second Amended and Restated Warner Music Group Corp. Senior Management Free Cash Flow Plan (the “Plan”) were settled or redeemed in accordance with the terms of the Plan. The Class A and Class B equity units held by certain participants in WMG Management Holdings, LLC (“Management LLC”) were redeemed in exchange for 18,265,183 shares of Class B Common Stock. These shares of Class B Common Stock converted to shares of Class A Common Stock upon exchange. The Company also issued a total of 4,321,259 additional shares of Class A Common Stock to settle the participants’ remaining deferred equity units previously issued under the Plan. In March 2021, the Compensation Committee of the Board of Directors of the Company approved an amendment to the Plan that allowed certain remaining Plan participants to redeem a portion of their vested Class B equity units of Management LLC. These Class B equity units were redeemed in exchange for a total of 968,920 shares of Class B Common Stock, which shares of Class B Common Stock converted to shares of Class A Common Stock upon the exchange.

In February 2021, Access converted 4,754,626 shares of Class B Common Stock to the same number of shares of Class A Common Stock, which it subsequently sold through open market sales, which is reflected as an exchange of Class B Common Stock for Class A Common Stock in the consolidated statements of equity for the three and six months ended March 31, 2021.

Earnings per Share

The consolidated statements of operations present basic and diluted earnings per share (“EPS”). Prior to the completion of the IPO, basic and diluted earnings per share were computed by dividing net income available to common stockholders by the weighted average number of outstanding common shares less shares issued for the exercise of the deferred equity units since these units were

mandatorily redeemable in cash. As such, the deferred equity units were excluded from the denominator of the basic and diluted EPS calculation prior to the IPO completion.

Subsequent to the completion of the IPO, the Company utilizes the two-class method to report earnings per share. The two-class method is an earnings allocation formula that determines earnings per share for each class of common stock according to dividends declared and participation rights in undistributed earnings. Undistributed earnings allocated to participating securities are subtracted from net income in determining net income attributable to common stockholders.

Stock-Based Compensation

The Company accounts for stock-based payments as required by ASC 718, Compensation—Stock Compensation (“ASC 718”). Under the recognition provision of ASC 718, the Company’s liability classified stock-based compensation costs are measured each reporting date until settlement. In February 2020, the Company filed a Form S-1 registration statement with the SEC in connection with the IPO, which required a change in accounting policy during the three months ended March 31, 2020 from the intrinsic value method to fair value method in determining the basis of measurement of its stock-based compensation liability.

Upon completion of the IPO in June 2020, the Plan was amended to remove the cash-settlement feature on all future redemptions. As a result, all awards previously issued under the Plan required settlement in equity. The participants in such plan were also allowed to sell a pro rata portion, consistent with Access’s percentage reduction in shares of Class B Common Stock as a result of the IPO, of their vested profits interests and acquired units of Management LLC, in the IPO through a “tag-along right.”

Under the provision of ASC 718, the Company determined the Plan was modified as of June 3, 2020, and as such, converted the awards from liability-classified to equity-classified. Prior to conversion, the Company performed a final measurement of its stock-based compensation liability under the fair value method. Subsequent to the amendment, the awards issued under the Plan will no longer be adjusted for changes in the value of the Company’s common stock. The Company will continue to incur non-cash stock-based compensation expense for awards that were unvested as of the modification date of the Plan and awards issued under the Omnibus Incentive Plan. During the three and six months ended March 31, 2021, the Company granted restricted stock units (“RSUs”) under the Omnibus Incentive Plan to eligible employees and executives.

The Company recognized approximately $15 million and $21 million of non-cash stock-based compensation expense for the three and six months ended March 31, 2021, respectively, of which $11 million and $17 million was recorded to additional paid-in capital, and a remaining $4 million has been classified as a share-based compensation liability as of March 31, 2021. The share-based liability represents executive awards that have not yet been granted under the Omnibus Incentive Plan, where a total value is known and settlement will occur in a variable number of RSUs.

Income Taxes

The Company uses the estimated annual effective tax rate method in computing its interim tax provision. Certain items, including those deemed to be unusual and infrequent are excluded from the estimated annual effective tax rate. In such cases, the actual tax expense or benefit is reported in the same period as the related item. Certain tax effects are also not reflected in the estimated annual effective tax rate, primarily certain changes in the realizability of deferred tax assets and uncertain tax positions.

New Accounting Pronouncements

Recently Adopted Accounting Pronouncements

In June 2016, the FASB issued ASU 2016-13, Financial Instruments—Credit Losses: Measurement of Credit Losses on Financial Instruments (“ASU 2016-13”). ASU 2016-13 requires that expected credit losses relating to financial assets measured on an amortized cost basis and available-for-sale debt securities be recorded through an allowance for credit losses. ASU 2016-13 limits the amount of credit losses to be recognized for available-for-sale debt securities to the amount by which carrying value exceeds fair value and also requires the reversal of previously recognized credit losses if fair value increases. The Company adopted ASU 2016-13 in the first quarter of fiscal 2021 and this adoption did not have a material impact on the Company’s consolidated financial statements.

Accounting Pronouncements Not Yet Adopted

In December 2019, the FASB issued ASU 2019-12, Simplifying the Accounting for Income Taxes (“ASU 2019-12”). This ASU eliminates certain exceptions to the general principles in ASC 740, Income Taxes. Specifically, it eliminates the exception to (1) the incremental approach for intraperiod tax allocation when there is a loss from continuing operations, and income or a gain from other items; (2) the requirement to recognize a deferred tax liability for equity method investments when a foreign subsidiary becomes an equity method investment; (3) the ability not to recognize a deferred tax liability for a foreign subsidiary when a foreign equity

method investment becomes a subsidiary; and (4) the general methodology for calculating income taxes in an interim period when a year-to-date loss exceeds the anticipated loss for the year. ASU 2019-12 also simplifies U.S. GAAP by making other changes. ASU 2019-12 will be effective for the annual periods beginning after December 15, 2021, and for interim periods beginning after December 15, 2022. Earlier adoption is permitted. The Company is evaluating the impact of the adoption of this standard on its consolidated financial statements.