UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, DC 20549

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Mallinckrodt public limited company

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*** Exercise Your Right to Vote *** Important Notice Regarding the Availability of Proxy Materials for the Shareholder Meeting to Be Held on May 15, 2019. MALLINCKRODT PLC C/O MALLINCKRODT PLC COMPANY SECRETARY 3 LOTUS PARK, THE CAUSEWAY STAINES-UPON-THAMES, SURREY TW18 3AG UNITED KINGDOM Meeting Information Meeting Type: Annual General Meeting For holders as of: March 11, 2019 Date: May 15, 2019 Time: 9:30 AM, Local Time Location: Sofitel London Heathrow Hotel Terminal 5, London Heathrow Airport London TW6 2GD United Kingdom 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. You may view the proxy materials online at www.proxyvote.com or easily request a paper copy (see reverse side). We encourage you to access and review all of the important information contained in the proxy materials before voting. proxy See the materials reverse and side voting of this instructions. notice to obtain

Before You Vote How to Access the Proxy Materials Proxy Materials Available to VIEW or RECEIVE: NOTICE AND PROXY STATEMENT ANNUAL REPORT ON FORM 10-K IRISH STATUTORY ACCOUNTS, INCLUDING RELATED REPORTS How to View Online: Have the information that is printed in the box marked by the arrow (located on the ?XXXX XXXX XXXX XXXX following page) and visit: www.proxyvote.com. How to Request and Receive a PAPER or E-MAIL Copy: If you want to receive a paper or e-mail copy of these documents, you must request one. There is NO charge for requesting a copy. Please choose one of the following methods to make your request: 1) BY INTERNET: www.proxyvote.com 2) BY TELEPHONE: 1-800-579-1639 3) BY E-MAIL*: sendmaterial@proxyvote.com * If requesting materials by e-mail, please send a blank e-mail with the information that is printed in the box marked by the arrow?XXXX XXXX XXXX XXXX (located on the following page) in the subject line. Requests, instructions and other inquiries sent to this e-mail address will NOT be forwarded to your investment advisor. Please make the request as instructed above on or before May 1, 2019 to facilitate timely delivery. How To Vote Please Choose One of the Following Voting Methods Vote In Person: Many shareholder meetings have attendance requirements including, but not limited to, the possession of an attendance ticket issued by the entity holding the meeting. Please check the meeting materials for any special requirements for meeting attendance. At the meeting, you will need to request a ballot to vote these shares. Vote By Internet: To vote now by Internet, go to www.proxyvote.com. Have the information that is printed in the box marked by the arrow ?XXXX XXXX XXXX XXXX (located on the following page) available and follow the instructions. Vote By Mail: You can vote by mail by requesting a paper copy of the materials, which will include a proxy card.

Voting Items The Board of Directors recommends a vote FOR the nominees listed under Item 1. The Board of Directors recommends a vote FOR Items 2 through 8. Item 1—Election of Directors Item 2—Approve, in a non-binding vote, the re-appointment of the Independent Auditors and to NOMINEES: authorize, in a binding vote, the Audit Committee to set the auditors’ remuneration. 1a. David R. Carlucci Item 3—Approve, in a non-binding advisory vote, the compensation of named executive officers. Item 4—Approve the authority of the Board to issue shares. 1b. J. Martin Carroll Item 5—Authorize the Company and/or any subsidiary to make market purchases or overseas 1c. Paul R. Carter market purchases of Company shares. Item 6—Approve the change of name of the Company. (Special Resolution). 1d. David Y. Norton Item 7—Approve the waiver of pre-emption rights. (Special Resolution). 1e. JoAnn A. Reed Item 8—Authorize the price range at which the Company can re-allot shares it holds as treasury shares. (Special Resolution). 1f. Angus C. Russell The Board of Directors recommends a vote AGAINST Items 9 and 10. 1g. Mark C. Trudeau Item 9—Shareholder Proposal Regarding Incentive Compensation Clawback. Item 10—Shareholder Proposal Regarding Report on Governance Measures. 1h. Anne C. Whitaker The Board of Directors recommends a vote FOR Item 11. 1i. Kneeland C. Youngblood, M.D. Item 11—Shareholder Proposal Regarding Report on Lobbying Activities. NOTE: Such other business as may properly come before the meeting or any adjournment thereof.