# EDGAR Filing Document

**Accession Number:** 0001330967
**File Stem:** 0000912938-26-000298
**Filing Date:** 2026-3
**Character Count:** 2208
**Document Hash:** 5ca95f3b2e7dfdedb1b597f2fa746b8e
**Contains OCR:** False
**Source Format:** 

## Filing Content

## Filing Summary
**0000912938-26-000298.hdr.sgml**: 20260305

**ACCESSION NUMBER**: 0000912938-26-000298

**CONFORMED SUBMISSION TYPE**: 497K

**PUBLIC DOCUMENT COUNT**: 2

**FILED AS OF DATE**: 20260305

**DATE AS OF CHANGE**: 20260305

**EFFECTIVENESS DATE**: 20260305

**FILER**: 

**COMPANY DATA:**
- **COMPANY CONFORMED NAME:** MFS SERIES TRUST XII
- **CENTRAL INDEX KEY:** 0001330967

**ORGANIZATION NAME:**
- **EIN:** 000000000
- **STATE OF INCORPORATION:** MA
- **FISCAL YEAR END:** 0430

**FILING VALUES:**
- **FORM TYPE:** 497K
- **SEC ACT:** 1933 Act
- **SEC FILE NUMBER:** 333-126328
- **FILM NUMBER:** 26724360

**BUSINESS ADDRESS:**
- **STREET 1:** 111 HUNTINGTON AVENUE
- **CITY:** BOSTON
- **STATE:** MA
- **ZIP:** 02199
- **BUSINESS PHONE:** 617-954-5000

**MAIL ADDRESS:**
- **STREET 1:** 111 HUNTINGTON AVENUE
- **CITY:** BOSTON
- **STATE:** MA
- **ZIP:** 02199

**FORMER COMPANY:**
- **FORMER CONFORMED NAME:** MFS Series Trust XII
- **DATE OF NAME CHANGE:** 20050622

## Series and Classes Contracts Data

### MFS Core Bond Fund (Series ID: S000076470)

| Class ID   | Class Name   | Ticker Symbol   |
|:---|:---|:---|
| C000236386 | R4           | MCBKX           |
| C000236387 | R6           | MCBMX           |
| C000236388 | R3           | MCBJX           |
| C000236389 | A            | MCBEX           |
| C000236390 | R1           | MCBGX           |
| C000236391 | I            | MCBFX           |
| C000236392 | C            | MCBCX           |
| C000236393 | R2           | MCBHX           |

![](img_502650f204b34f1.jpg)

SUPPLEMENT TO THE SUMMARY PROSPECTUS

*The date of this supplement is March 5, 2026.*

## MFS <sup>®</sup> Core Bond Fund

## MFS <sup>®</sup> Total Return Fund

## MFS <sup>®</sup> Total Return Series
**Effective March 31, 2026, the following is added to the table in the sub-section entitled "Portfolio Manager(s)" under the main heading entitled "Summary of Key Information":**

---

| | | |
|:---|:---|:---|
| &nbsp;&nbsp;**Portfolio Manager** | &nbsp;&nbsp;**Since** | &nbsp;&nbsp;&nbsp;**Title** |
| &nbsp;&nbsp;Philipp Burgener | &nbsp;&nbsp;March 2026 | &nbsp;&nbsp;&nbsp;Investment Officer of MFS |

---

MULTI-SUM-SUP-III-030526

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