UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

SCHEDULE 14A

Proxy Statement Pursuant to Section 14(a) of the

Securities Exchange Act of 1934

(Amendment No.    )

Filed by the Registrant  ☑                             Filed by a Party Other than the Registrant  ☐

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☐	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 Pursuant to § 240.14a-12

HOUGHTON MIFFLIN HARCOURT COMPANY

(Name of Registrant as Specified In Its Charter)

(Name of Person(s) Filing Proxy Statement, if other than the Registrant)

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Important Notice Regarding the Availability of Proxy Materials for Houghton Mifflin Harcourt Company P.O. BOX 8016, CARY, NC 27512-9903 Stockholders Meeting to be held on May 14, 2021 For Stockholders as of March 15, 2021 This communication presents only an overview of the more complete proxy materials that are available to you on the Internet. This is not a ballot. You cannot use this notice to vote your shares. We encourage you to access and review all of the important information contained in the proxy materials before voting. To view the proxy materials go to: www.proxydocs.com/HMHC To vote your proxy while visiting this site, you will need the 12 digit control number in the box below. Under United States Securities and Exchange Commission rules, proxy materials do not have to be delivered in paper. Proxy materials can be distributed by making them available on the internet. CONTROL NUMBER For a convenient way to view proxy materials and VOTE go to www.proxydocs.com/HMHC Have the 12 digit control number located in the shaded box above available when you access the website and follow the instructions. if you want to receive a paper or e-mail copy of the proxy material, you must request one. There is no charge to you for requesting a copy. In order to receive a paper package in time for this year’s shareholder meeting, you must make this request on or before May 03, 2021 To order paper materials, use one of the following methods. INTERNET www.investorelections.com/HMHC  TELEPHONE(866) 648-8133 * E MAIL paper@investorelections.com When requesting via the internet or telephone you will need the 12 digit control number located in the shaded box above. * If requesting material by e-mail, please send a blank e-mail with the 12 digit control number (located above) in the subject line. No other requests, instructions or other inquiries should be included with your e-mail requesting material. Houghton Mifflin Harcourt Company Meeting Information Meeting Materials: Notice of Meeting and Proxy Statement & Annual Report or Form 10-K Meeting Type: Annual Meeting of Stockholders Date: Friday, May 14, 2021 Time:08:00 AM, Eastern Time Place: www.proxydocs.com/HMHC You must pre-register to attend the meeting online and/or participate at the email address indicated. SEE REVERSE FOR FULL AGENDA  Copyright 2021 Mediant Communications Inc. All Rights Reserved

Houghton Mifflin Harcourt Company Annual Meeting of Stockholders THE BOARD OF DIRECTORS RECOMMENDS A VOTE FOR PROPOSAL(S) 1, 2, 3, 4. PROPOSAL 1. ELECTION OF NINE DIRECTORS: 1.01 Jean-Claude Brizard 1.02 L. Gordon Crovitz 1.03 Jean S. Desravines 1.04 Lawrence K. Fish  1.05 Jill A. Greenthal 1.06 John F. Killian 1.07 John J. Lynch, Jr. 1.08 John R. McKernan, Jr. 1.09 Tracey D. Weber 2. Advisory Approval of Compensation of Named Executive Officers 3. Approval of the adoption of the Amended and Restated Employee Stock Purchase Plan 4. Ratification of Appointment of the Company’s Independent Registered Public Accounting Firm for Fiscal Year 2021