UPDATE: The USPTO has delayed the date when DOCX Documents are required to avoid a surcharge to JUNE 30, 2023.

For many U.S. non-provisional patent applications filed on or after June 3, 2023, the USPTO will require payment of a surcharge fee if the specification, claims, and abstract are not filed in DOCX format. The non-DOCX surcharge fee is $400. The non-DOCX surcharge fee applies to non-provisional applications filed under 35 U.S.C. §111, including Paris Convention and non-convention applications. The fee will apply to divisionals, continuations, continuations-in-part, and PCT bypass-continuations. The fee will not apply to PCT National Stage applications, Provisional Patent applications, or Design Patent applications.

https://www.federalregister.gov/public-inspection/2023-06289/setting-and-adjusting-patent-fees-during-fiscal-year-2020?utm_campaign=subscriptioncenter&utm_content=&utm_medium=email&utm_name=&utm_source=govdelivery&utm_term

The USPTO also recently extended the period during which patent applicants have the option to submit an applicant generated PDF along with the validated DOCX file. We may file both DOCX and PDF Specifications without paying the surcharge until June 30, 2023.

Federal Register :: Extension of Period To Allow Submission of a PDF With a Patent Application Filed in DOCX Format