USPTO Begins New Trademark Serial Number Series

The United States Patent and Trademark Office implemented a change to its trademark application numbering system on July 18, 2026. New serial numbers for applications filed under sections 1 or 44 of the Trademark Act now begin with the prefix 50 while retaining the standard eight-digit length. The update affects filings processed after the transition date and aims to support ongoing system modernization. Existing applications retain their original serial numbers without alteration. Practitioners and brand owners filing new U.S. applications should note the updated format when tracking cases or corresponding with the office. The change does not alter examination procedures or substantive trademark law.

This administrative update follows other recent USPTO initiatives, including homepage redesigns and guidance on name-image-likeness protections.