Company: ACCO
Filing Date: 2025-03-28
Form Type: DEFA14A
Source: 0000950170-25-046401
Chunk: 0

Company: ACCO BRANDS Corp
Filing Date: 2025-03-28
Form: DEFA14A
Chunk 0
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UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D. C. 20549 SCHEDULE 14A INFORMATION Proxy Statement Pursuant to Section 14(a) of the Securities Exchange Act of 1934

| Filed by the Registrant ☒ | ​ | ​ | Filed by a party other than the Registrant  ☐ |

Check the appropriate box:

| ☐ | ​ | ​ | Preliminary Proxy Statement                                                     |
| ☐ | ​ | ​ | Confidential, for Use of the Commission Only (as permitted by Rule 14a-6(e)(2)) |
| ☐ | ​ | ​ | Definitive Proxy Statement                                                      |
| ☒ | ​ | ​ | Definitive Additional Materials                                                 |
| ☐ | ​ | ​ | Soliciting Material under §240.14a-12                                           |

ACCO BRANDS CORPORATION (Name of Registrant as Specified in Its Charter) (Name of Person(s) Filing Proxy Statement, if other than the Registrant) Payment of Filing Fee (Check all boxes that apply):

| ☒ | ​ | ​ | No fee required                                                                                     |
| ☐ | ​ | ​ | Fee paid previously with preliminary materials                                                      |
| ☐ | ​ | ​ | Fee computed on table in exhibit required by Item 25(b) per Exchange Act Rules 14a-6(i)(1) and 0-11 |

ACCO BRANDS CORPORATION Important Notice Regarding the Availability of Proxy Materials for the
Annual Meeting of Stockholders to be Held Virtually on May 20, 2025 You are receiving this communication because you hold shares in the company named above. This is not a ballot. You cannot use this notice to vote these shares. This communication presents only an overview of the more complete proxy materials that are available to you on the Internet. We encourage you to access and review all of the important information contained in the proxy materials before voting. The Proxy Statement and 2024 Annual Report on Form 10-K are available at https://web.viewproxy.com/ACCO/2025 . If you want to receive a paper or e-mail copy of these documents, you must request one. There is no charge to you for a copy. Please make your request for a copy as instructed below on or before May 12, 2025 to facilitate timely delivery. Important information regarding the Internet availability of the company’s proxy materials, instructions for accessing your proxy materials and voting online and instructions for requesting paper or