N-CSR

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

FORM N-CSR

CERTIFIED SHAREHOLDER REPORT OF

REGISTERED MANAGEMENT INVESTMENT COMPANIES

Investment Company Act file number 811-21780

MFS SERIES TRUST XII

(Exact name of registrant as specified in charter)

111 Huntington Avenue, Boston, Massachusetts 02199

(Address of principal executive offices) (Zip code)

Christopher R. Bohane

Massachusetts Financial Services Company

111 Huntington Avenue

Boston, Massachusetts 02199

(Name and address of agents for service)

Registrant’s telephone number, including area code: (617) 954-5000

Date of fiscal year end: October 31*

Date of reporting period: October 31, 2019

* This Form N-CSR pertains to the following series of the Registrant: MFS Equity Opportunities Fund. Effective as of the close of business on October 25, 2019, MFS Equity Opportunities Fund was acquired by MFS Core Equity Fund, a series of MFS Series Trust I, and MFS Equity Opportunities Fund terminated as a series of the Registrant. The remaining series of the Registrant have fiscal year ends of April 30.

ITEM 1. REPORTS TO STOCKHOLDERS.

No report to stockholders is included in this Item 1 for MFS Equity Opportunities Fund since there were no shareholders of MFS Equity Opportunities Fund as of the reporting period end. Effective as of the close of business on October 25, 2019, MFS Equity Opportunities Fund was acquired by MFS Core Equity Fund, a series of MFS Series Trust I, and MFS Equity Opportunities Fund terminated as a series of the Registrant.

ITEM 2. CODE OF ETHICS.

The Registrant has adopted a Code of Ethics (the “Code”) pursuant to Section 406 of the Sarbanes-Oxley Act and as defined in Form N-CSR that applies to the Registrant’s principal executive officer and principal financial and accounting officer. During the period covered by this report, the Registrant has not amended any provision in the Code that relates to an element of the Code’s definition enumerated in paragraph (b) of Item 2 of this Form N-CSR. During the period covered by this report, the Registrant did not grant a waiver, including an implicit waiver, from any provision of the Code.

A copy of the Code is filed as an exhibit to this Form N-CSR.

ITEM 3. AUDIT COMMITTEE FINANCIAL EXPERT.

Messrs. Steven E. Buller, Michael Hegarty, James Kilman, and Clarence Otis, Jr. and Ms. Maryanne L. Roepke, members of the Audit Committee, have been determined by the Board of Trustees in their reasonable business judgment to meet the definition of “audit committee financial expert” as such term is defined in Form N-CSR. In addition, Messrs. Buller, Hegarty, Kilman, and Otis and Ms. Roepke are “independent” members of the Audit Committee (as such term has been defined by the Securities and Exchange Commission in regulations implementing Section 407 of the Sarbanes-Oxley Act of 2002). The Securities and Exchange Commission has stated that the designation of a person as an audit committee financial expert pursuant to this Item 3 on the Form N-CSR does not impose on such a person any duties, obligations or liability that are greater than the duties, obligations or liability imposed on such person as a member of the Audit Committee and the Board of Trustees in the absence of such designation or identification.

As of December 31, 2019, Mr. Hegarty will retire as Trustee and will no longer be a member of the Audit Committee.

ITEM 4. PRINCIPAL ACCOUNTANT FEES AND SERVICES.

Items 4(a) through 4(d) and 4(g):

The Board of Trustees has appointed Ernst & Young LLP (“E&Y”) to serve as independent accountants to the series of the Registrant (the series referred to as the “Fund”). The tables below set forth the audit fees billed to the Fund as well as fees for non-audit services provided to the Fund and/or to the Fund’s investment adviser, Massachusetts Financial Services Company (“MFS”) and to various entities either controlling, controlled by, or under common control with MFS that provide ongoing services to the Fund (“MFS Related Entities”).

For the fiscal years ended October 31, 2019 and 2018, audit fees billed to the Fund by E&Y were as follows:

	Audit Fees
	2019		2018
Fees billed by E&Y:
MFS Equity Opportunities Fund+		0		38,543

For the fiscal years ended October 31, 2019 and 2018, fees billed by E&Y for audit-related, tax and other services provided to the Fund and for audit-related, tax and other services provided to MFS and MFS Related Entities were as follows:

	Audit-Related  Fees1				Tax Fees2				All Other Fees3
	2019		2018		2019		2018		2019		2018
Fees billed by E&Y:
To MFS Equity Opportunities Fund+		2,500		0		7,772		8,050		1,107		1,140
	Audit-Related Fees1				Tax Fees2				All Other Fees3
	2019		2018		2019		2018		2019		2018
Fees billed by E&Y:
To MFS and MFS Related Entities of MFS Equity Opportunities Fund*+		1,679,277		1,728,076		0		0		104,750		34,150

	Aggregate Fees for Non-audit Services
	2019		2018
Fees Billed by E&Y:
To MFS Equity Opportunities Fund, MFS and MFS Related Entities#+		2,020,606		1,969,116

+ MFS Equity Opportunities Fund was reorganized into the MFS Core Equity Fund, a series of MFS Series Trust I, effective as of the close of business on October 25, 2019.

* This amount reflects the fees billed to MFS and MFS Related Entities for non-audit services relating directly to the operations and financial reporting of the Fund (portions of which services also related to the operations and financial reporting of other funds within the MFS Funds complex).

# This amount reflects the aggregate fees billed by E&Y for non-audit services rendered to the Fund and for non-audit services rendered to MFS and the MFS Related Entities.

¹  The fees included under “Audit-Related Fees” are fees related to assurance and related services that are reasonably related to the performance of the audit or review of financial statements, but not reported under “Audit Fees,” including accounting consultations, agreed-upon procedure reports, attestation reports, comfort letters and internal control reviews.

²  The fees included under “Tax Fees” are fees associated with tax compliance, tax advice and tax planning, including services relating to the filing or amendment of federal, state or local income tax returns, regulated investment company qualification reviews and tax distribution and analysis.

³  The fees included under “All Other Fees” are fees for products and services provided by E&Y other than those reported under “Audit Fees,” “Audit-Related Fees” and “Tax Fees,” including fees for services related to review of internal controls and review of Rule 38a-1 compliance program.

Item 4(e)(1):

Set forth below are the policies and procedures established by the Audit Committee of the Board of Trustees relating to the pre-approval of audit and non-audit related services:

To the extent required by applicable law, pre-approval by the Audit Committee of the Board is needed for all audit and permissible non-audit services rendered to the Funds and all permissible non-audit services rendered to MFS or MFS Related Entities if the services relate directly to the operations and financial reporting of the Registrant. Pre-approval is

currently on an engagement-by-engagement basis. In the event pre-approval of such services is necessary between regular meetings of the Audit Committee and it is not practical to wait to seek pre-approval at the next regular meeting of the Audit Committee, pre-approval of such services may be referred to the Chair of the Audit Committee for approval; provided that the Chair may not pre-approve any individual engagement for such services exceeding $50,000 or multiple engagements for such services in the aggregate exceeding $100,000 in each period between regular meetings of the Audit Committee. Any engagement pre-approved by the Chair between regular meetings of the Audit Committee shall be presented for ratification by the entire Audit Committee at its next regularly scheduled meeting.

Item 4(e)(2):

None, or 0%, of the services relating to the Audit-Related Fees, Tax Fees and All Other Fees paid by the Fund and MFS and MFS Related Entities relating directly to the operations and financial reporting of the Registrant disclosed above were approved by the audit committee pursuant to paragraphs (c)(7)(i)(C) of Rule 2-01 of Regulation S-X (which permits audit committee approval after the start of the engagement with respect to services other than audit, review or attest services, if certain conditions are satisfied).

Item 4(f):

Not applicable.

Item 4(h):

The Registrant’s Audit Committee has considered whether the provision by a Registrant’s independent registered public accounting firm of non-audit services to MFS and MFS Related Entities that were not pre-approved by the Committee (because such services did not relate directly to the operations and financial reporting of the Registrant) was compatible with maintaining the independence of the independent registered public accounting firm as the Registrant’s principal auditors.

ITEM 5. AUDIT COMMITTEE OF LISTED REGISTRANTS.

Not applicable to the Registrant.

ITEM 6. INVESTMENTS

No schedule of investments for MFS Equity Opportunities Fund is included in this Item 6 since there were no shareholders of MFS Equity Opportunities Fund as of the reporting period end. Effective as of the close of business on October 25, 2019, MFS Equity Opportunities Fund was acquired by MFS Core Equity Fund, a series of MFS Series Trust I, and MFS Equity Opportunities Fund terminated as a series of the Registrant.

ITEM 7. DISCLOSURE OF PROXY VOTING POLICIES AND PROCEDURES FOR CLOSED-END MANAGEMENT INVESTMENT COMPANIES.

Not applicable to the Registrant.

ITEM 8. PORTFOLIO MANAGERS OF CLOSED-END MANAGEMENT INVESTMENT COMPANIES.

Not applicable to the Registrant.

ITEM 9. PURCHASES OF EQUITY SECURITIES BY CLOSED-END MANAGEMENT INVESTMENT COMPANY AND AFFILIATED PURCHASERS.

Not applicable to the Registrant.

ITEM 10. SUBMISSION OF MATTERS TO A VOTE OF SECURITY HOLDERS.

There were no material changes to the procedures by which shareholders may send recommendations to the Board for nominees to the Registrant’s Board since the Registrant last provided disclosure as to such procedures in response to the requirements of Item 407 (c)(2)(iv) of Regulation S-K or this Item.

ITEM 11. CONTROLS AND PROCEDURES.

(a) Based upon their evaluation of the effectiveness of the registrant’s disclosure controls and procedures (as defined in Rule 30a-3(c) under the Investment Company Act of 1940 (the “Act”)) as conducted within 90 days of the filing date of this report on Form N-CSR, the registrant’s principal financial officer and principal executive officer have concluded that those disclosure controls and procedures provide reasonable assurance that the material information required to be disclosed by the registrant on this report is recorded, processed, summarized and reported within the time periods specified in the Securities and Exchange Commission’s rules and forms.

(b) There were no changes in the registrant’s internal controls over financial reporting (as defined in Rule 30a-3(d) under the Act) that occurred during the period covered by the report that have materially affected, or are reasonably likely to materially affect, the registrant’s internal control over financial reporting.

ITEM 12. DISCLOSURE OF SECURITIES LENDING ACTIVITIES FOR CLOSED-END MANAGEMENT INVESTMENT COMPANIES.

Not applicable to the Registrant.

ITEM 13. EXHIBITS.

(a)	(1)     Any code of ethics, or amendment thereto, that is the subject of the disclosure required by Item 2, to the extent that the registrant intends to satisfy the Item 2 requirements through filing of an exhibit: Attached hereto as EX-99.COE.
	(2)     A separate certification for each principal executive officer and principal financial officer of the registrant as required by Rule 30a-2(a) under the Act (17 CFR 270.30a-2): Attached hereto as EX-99.302CERT.
	(3)     Any written solicitation to purchase securities under Rule 23c-1 under the Act (17 CFR 270.23c-1) sent or given during the period covered by the report by or on behalf of the registrant to 10 or more persons. Not applicable.
	(4)     Change in the registrant’s independent public accountant. Not applicable.
(b)	If the report is filed under Section 13(a) or 15(d) of the Exchange Act, provide the certifications required by Rule 30a-2(b) under the Act (17 CFR 270.30a-2(b)), Rule 13a-14(b) or Rule 15d-14(b) under the Exchange Act (17 CFR 240.13a-14(b) or 240.15d-14(b)) and Section 1350 of Chapter 63 of Title 18 of the United States Code (18 U.S.C. 1350) as an exhibit. A certification furnished pursuant to this paragraph will not be deemed “filed” for the purposes of Section 18 of the Exchange Act (15 U.S.C. 78r), or otherwise subject to the liability of that section. Such certification will not be deemed to be incorporated by reference into any filing under the Securities Act of 1933 or the Exchange Act, except to the extent that the registrant specifically incorporates it by reference. Attached hereto as EX-99.906CERT.

Notice

A copy of the Declaration of Trust, as amended, of the Registrant is on file with the Secretary of State of The Commonwealth of Massachusetts and notice is hereby given that this instrument is executed on behalf of the Registrant by an officer of the Registrant as an officer and not individually and the obligations of or arising out of this instrument are not binding upon any of the Trustees or shareholders individually, but are binding only upon the assets and property of the respective constituent series of the Registrant.

SIGNATURES

Pursuant to the requirements of the Securities Exchange Act of 1934 and the Investment Company Act of 1940, the registrant has duly caused this report to be signed on its behalf by the undersigned, thereunto duly authorized.

(Registrant): MFS SERIES TRUST XII

By (Signature and Title)*	DAVID L. DILORENZO
	David L. DiLorenzo, President

Date: December 16, 2019

Pursuant to the requirements of the Securities Exchange Act of 1934 and the Investment Company Act of 1940, this report has been signed below by the following persons on behalf of the registrant and in the capacities and on the dates indicated.

By (Signature and Title)*	DAVID L. DILORENZO
	David L. DiLorenzo, President (Principal Executive Officer)

Date: December 16, 2019

By (Signature and Title)*	JAMES O. YOST
	James O. Yost, Treasurer (Principal Financial Officer and Accounting Officer)

Date: December 16, 2019

* Print name and title of each signing officer under his or her signature.

EX-99.(12)(A)(1)

EX 99.COE

Code of Ethics for Principal Executive and Principal Financial Officers

Effective February 13, 2018

I. Policy Purpose and Summary

Section 406 of the Sarbanes-Oxley Act requires that each MFS Fund registered under the Investment Company Act of 1940 disclose whether or not it has adopted a code of ethics for senior financial officers, applicable to its principal financial officer and principal accounting officer.

II. Overview

A. Covered Officers/Purpose of the Code

This code of ethics (this “Code”) has been adopted by the funds (collectively, “Funds” and each, “Fund”) under supervision of the MFS Funds Board (the “Board”) and applies to the Funds’ Principal Executive Officer and Principal Financial Officer (the “Covered Officers” each of whom is set forth in Exhibit A) for the purpose of promoting:

• honest and ethical conduct, including the ethical handling of actual or apparent conflicts of interest between personal and professional relationships;

• full, fair, accurate, timely and understandable disclosure in reports and documents that the Funds file with, or submit to, the Securities and Exchange Commission (“SEC”) and in other public communications made by the Funds;

• compliance by the Funds with applicable laws and governmental rules and regulations;

• the prompt internal reporting of violations of the Code to an appropriate person or persons identified in the Code; and

• accountability for adherence to the Code.

B. Conduct Guidelines

Each Covered Officer should adhere to a high standard of business ethics and should be sensitive to situations that may give rise to actual as well as apparent conflicts of interest. In addition, each Covered Officer should not place his or her personal interests ahead of the Funds’ interests and should endeavor to act honestly and ethically. In furtherance of the foregoing, each Covered Officer must:

• not use his or her personal influence or personal relationships improperly to influence investment decisions or financial reporting for any Fund whereby the Covered Officer would benefit personally to the detriment of the Fund; and

• not cause a Fund to take action, or fail to take action, for the individual personal benefit of the Covered Officer rather than the benefit the Fund.

The following activities, which could create the appearance of a conflict of interest, are permitted only with the approval of the Funds’ Chief Legal Officer (“CLO”):

• service as a director on the board of any “for profit” company other than the board of the Funds’ investment adviser or its subsidiaries or board of a pooled investment vehicle sponsored by the Funds’ investment adviser or its subsidiaries;

• running for political office;

• the receipt of any Fund business-related gift or any entertainment from any company with which a Fund has current or prospective business dealings unless such gift or entertainment is permitted by the gifts and entertainment policy of the Funds’ investment adviser;

• any material ownership interest in, or any consulting or employment relationship with, any Fund service providers (e.g., custodian banks, audit firms), other than the Funds’ investment adviser, principal underwriter, administrator or any affiliated person thereof;

• a direct or indirect financial interest in commissions, transaction charges or spreads paid by a Fund for effecting portfolio transactions or for selling or redeeming shares, other than an interest arising from the Covered Officer’s employment or securities ownership.

C. Disclosure and Compliance

• Each Covered Officer should familiarize himself or herself with the disclosure requirements generally applicable to the Funds;

• each Covered Officer should not knowingly misrepresent, or cause others to misrepresent, facts about a Fund to others, whether within or outside the Fund, including to the Fund’s trustees and auditors, and to governmental regulators and self-regulatory organizations;

• each Covered Officer should, to the extent appropriate within his or her area of Fund responsibility, consult with other officers and employees of the Funds and the adviser with the goal of promoting full, fair, accurate, timely and understandable disclosure in the reports and documents the Funds file with, or submit to, the SEC and in other public communications made by the Funds; and

• it is the responsibility of each Covered Officer to promote compliance within his or her area of Fund responsibility with the standards and restrictions imposed by applicable laws, rules and regulations.

D. Reporting and Accountability

Each Covered Officer must:

• upon adoption of the Code (or thereafter as applicable, upon becoming a Covered Officer), affirm in writing to the Board that he or she has received, read, and understands the Code;

• annually thereafter affirm to the Board that he or she has complied with the requirements of the Code;

• annually report to the CLO affiliations and relationships which are or may raise the appearance of a conflict of interest with the Covered Officer’s duties to the Funds, as identified in the annual Trustee and Officer Questionnaire;

• not retaliate against any other Covered Officer or any officer or employee of the Funds or their affiliated persons for reports of potential violations that are made in good faith; and

• notify the CLO promptly if he or she knows of any violation of this Code. Failure to do so is itself a violation of this Code.

The CLO is responsible for applying this Code to specific situations in which questions are presented under it, granting waivers upon consultation with the Board or its designee, investigating violations, and has the authority to interpret this Code in any particular situation. The CLO will report requests for waivers to the Board (or a designee thereof) promptly upon receipt of a waiver request and will periodically report to the Board any approvals granted since the last report.

The CLO will take all appropriate action to investigate any potential violations reported to him or her and to report any violations to the Board. If the Board concurs that a violation has occurred, it will consider appropriate action, which may include review of, and appropriate modifications to, applicable policies and procedures; notification to appropriate personnel of the investment adviser or its board; or a recommendation to dismiss the Covered Officer.

Any changes to or waivers of this Code will, to the extent required, be disclosed as provided by SEC rules.

E. Confidentiality

All reports and records prepared or maintained pursuant to this Code and under the direction of the CLO will be considered confidential and shall be maintained and protected accordingly. Except as otherwise required by law or this Code, such matters shall not be disclosed to anyone other than the Funds’ Board, its counsel, counsel to the Board’s independent trustees and senior management and the board of directors of the Fund’s investment adviser and its counsel.

F. Internal Use

The Code is intended solely for the internal use by the Funds and does not constitute an admission, by or on behalf of any Fund, as to any fact, circumstance, or legal conclusion.

III. Supervision

The Board of Trustees of the Funds, including a majority of the Trustees who are not “interested persons” (as defined in the 1940 Act) of the Funds, shall review no less frequently than annually, a report from the CLO regarding the affirmations of the principal executive officer and the principal financial officer as to compliance with this Code.

IV. Interpretation and Escalation

Breaches of the Code are reviewed by the CLO and communicated to the Board of Trustees of the affected Fund(s). Interpretations of this Policy shall be made from time to time by the CLO, as needed, and questions regarding the application of this Policy to a specific set of facts are escalated to the CLO.

V. Authority

Section 406 of the Sarbanes-Oxley Act.

VI. Monitoring

Adherence to this policy is monitored by the CLO.

VII. Related Policies

This Code shall be the sole code of ethics adopted by the Funds for purposes of Section 406 of the Sarbanes-Oxley Act and the rules and forms applicable to registered investment companies thereunder. Insofar as other policies or procedures of the Funds, the Funds’ adviser, principal underwriter, or other service providers govern or purport to govern the behavior or activities of the Covered Officers who are subject to this Code, they are superseded by this Code to the extent that they overlap or conflict with the provisions of this Code. The Funds’ and their investment adviser’s codes of ethics under Rule 17j-1 under the Investment Company Act and any other codes or policies or procedures adopted by the Funds or their investment adviser or other service providers are separate requirements and are not part of this Code.

VIII. Amendment

Any amendments to this Code, other than amendments to Exhibit A, must be approved or ratified by a majority vote of the Board, including a majority of independent trustees.

IX. Recordkeeping

All required books, records and other documentation shall be retained in accordance with MFS’ related record retention policy.

Additional procedures may need to be implemented by departments to properly comply with this policy.

Exhibit A

As of January 1, 2017

Persons Covered by this Code of Ethics

Funds’ Principal Executive Officer: David L. DiLorenzo

Funds’ Principal Financial Officer: James O. Yost

EX-99.CERT

EX-99.302CERT

MFS SERIES TRUST XII

CERTIFICATION PURSUANT TO SECTION 302 OF THE SARBANES-OXLEY ACT

I, James O. Yost, certify that:

1. I have reviewed this report on Form N-CSR of MFS Series Trust XII;

2. Based on my knowledge, this report does not contain any untrue statement of a material fact or omit to state a material fact necessary to make the statements made, in light of the circumstances under which such statements were made, not misleading with respect to the period covered by this report;

3. Based on my knowledge, the financial statements, and other financial information included in this report, fairly present in all material respects the financial condition, results of operations, changes in net assets, and cash flows (if the financial statements are required to include a statement of cash flows) of the registrant as of, and for, the periods presented in this report;

4. The registrant’s other certifying officer and I are responsible for establishing and maintaining disclosure controls and procedures (as defined in Rule 30a-3(c) under the Investment Company Act of 1940) and internal control over financial reporting (as defined in Rule 30a-3(d) under the Investment Company Act of 1940) for the registrant and have:

a. Designed such disclosure controls and procedures, or caused such disclosure controls and procedures to be designed under our supervision, to ensure that material information relating to the registrant, including its consolidated subsidiaries, is made known to us by others within those entities, particularly during the period in which this report is being prepared;

b. Designed such internal control over financial reporting, or caused such internal control over financial reporting to be designed under our supervision, to provide reasonable assurance regarding the reliability of financial reporting and the preparation of financial statements for external purposes in accordance with generally accepted accounting principles;

c. Evaluated the effectiveness of the registrant’s disclosure controls and procedures and presented in this report our conclusions about the effectiveness of the disclosure controls and procedures as of a date within 90 days prior to the filing date of this report based on such evaluation; and

d. Disclosed in this report any change in the registrant’s internal control over financial reporting that occurred during the period covered by the report that has materially affected, or is reasonably likely to materially affect, the registrant’s internal control over financial reporting; and

5. The registrant’s other certifying officer and I have disclosed to the registrant’s auditors and the audit committee of the registrant’s board of directors (or persons performing the equivalent functions):

a. All significant deficiencies and material weaknesses in the design or operation of internal control over financial reporting which are reasonably likely to adversely affect the registrant’s ability to record, process, summarize, and report financial information; and

b. Any fraud, whether or not material, that involves management or other employees who have a significant role in the registrant’s internal control over financial reporting.

Date: December 16, 2019	JAMES O. YOST
	James O. Yost Treasurer (Principal Financial Officer and Accounting Officer)

EX-99.302CERT

MFS SERIES TRUST XII

CERTIFICATION PURSUANT TO SECTION 302 OF THE SARBANES-OXLEY ACT

I, David L. DiLorenzo, certify that:

1. I have reviewed this report on Form N-CSR of MFS Series Trust XII;

2. Based on my knowledge, this report does not contain any untrue statement of a material fact or omit to state a material fact necessary to make the statements made, in light of the circumstances under which such statements were made, not misleading with respect to the period covered by this report;

3. Based on my knowledge, the financial statements, and other financial information included in this report, fairly present in all material respects the financial condition, results of operations, changes in net assets, and cash flows (if the financial statements are required to include a statement of cash flows) of the registrant as of, and for, the periods presented in this report;

4. The registrant’s other certifying officer and I are responsible for establishing and maintaining disclosure controls and procedures (as defined in Rule 30a-3(c) under the Investment Company Act of 1940) and internal control over financial reporting (as defined in Rule 30a-3(d) under the Investment Company Act of 1940) for the registrant and have:

a. Designed such disclosure controls and procedures, or caused such disclosure controls and procedures to be designed under our supervision, to ensure that material information relating to the registrant, including its consolidated subsidiaries, is made known to us by others within those entities, particularly during the period in which this report is being prepared;

b. Designed such internal control over financial reporting, or caused such internal control over financial reporting to be designed under our supervision, to provide reasonable assurance regarding the reliability of financial reporting and the preparation of financial statements for external purposes in accordance with generally accepted accounting principles;

c. Evaluated the effectiveness of the registrant’s disclosure controls and procedures and presented in this report our conclusions about the effectiveness of the disclosure controls and procedures as of a date within 90 days prior to the filing date of this report based on such evaluation; and

d. Disclosed in this report any change in the registrant’s internal control over financial reporting that occurred during the period covered by the report that has materially affected, or is reasonably likely to materially affect, the registrant’s internal control over financial reporting; and

5. The registrant’s other certifying officer and I have disclosed to the registrant’s auditors and the audit committee of the registrant’s board of directors (or persons performing the equivalent functions):

a. All significant deficiencies and material weaknesses in the design or operation of internal control over financial reporting which are reasonably likely to adversely affect the registrant’s ability to record, process, summarize, and report financial information; and

b. Any fraud, whether or not material, that involves management or other employees who have a significant role in the registrant’s internal control over financial reporting.

Date: December 16, 2019	DAVID L. DILORENZO
	David L. DiLorenzo President (Principal Executive Officer)

EX-99.906CERT

EX-99.906CERT

MFS SERIES TRUST XII

CERTIFICATION PURSUANT TO SECTION 906 OF THE SARBANES-OXLEY ACT

I, James O. Yost, certify that, to my knowledge:

1. The Form N-CSR (the “Report”) of MFS Series Trust XII (the “Registrant”) fully complies for the period covered by the Report with the requirements of Section 13(a) or 15(d) of the Securities Exchange Act of 1934; and

2. The information contained in the Report fairly presents, in all material respects, the financial condition and results of operations of the Registrant.

Date: December 16, 2019	JAMES O. YOST
	James O. Yost Treasurer (Principal Financial Officer and Accounting Officer)

A signed original of this written statement required by Section 906 has been provided to the Registrant and will be retained by the Registrant and furnished to the Securities and Exchange Commission or its staff upon request.

EX-99.906CERT

MFS SERIES TRUST XII

CERTIFICATION PURSUANT TO SECTION 906 OF THE SARBANES-OXLEY ACT

I, David L. DiLorenzo, certify that, to my knowledge:

1. The Form N-CSR (the “Report”) of MFS Series Trust XII (the “Registrant”) fully complies for the period covered by the Report with the requirements of Section 13(a) or 15(d) of the Securities Exchange Act of 1934; and

2. The information contained in the Report fairly presents, in all material respects, the financial condition and results of operations of the Registrant.

Date: December 16, 2019	DAVID L. DILORENZO
	David L. DiLorenzo President (Principal Executive Officer)

A signed original of this written statement required by Section 906 has been provided to the Registrant and will be retained by the Registrant and furnished to the Securities and Exchange Commission or its staff upon request.