Tax insight

New US Postal Service rules could have implications for tax filers

Insight
5 minute read
January 23, 2026

What happened?

Effective December 24, 2025, the US Postal Service (Postal Service, or USPS) adopted new rules regarding postmarks, explaining that postmarks may be applied at a regional processing center, rather than at the local post office where mail is dropped off. As a result, the postmark date on a mailed item may be later than the date it was presented to the Postal Service. While the Postal Service notes that this is not a change in USPS practice, it has made adjustments to USPS transportation operations that will result in some mail pieces not arriving at originating processing facilities on the same day that they are mailed.

[Postal Service, 39 CFR Part 111, Postmarks and Postal Possession, Final Rule, Federal Register / Vol. 90, No. 224 (11/24/2025); Domestic Mail Manual, updated 1/18/2026]

Why is it relevant?

For federal, state, and local tax filings or payments where timeliness is determined by the postmark date, the potential lack of alignment between the date the USPS accepts possession of a mailed item and the postmark date represents a risk that an item dropped off on or near a due date could receive a postmark dated after the deadline.

Actions to consider

Taxpayers should consider using electronic filing or payment options when available or mailing time-sensitive filings and payments earlier and maintaining proof of mailing. As explained in the updated rules, taxpayers also can request a manual postmark at the local post office at the time of mailing or use a Certificate of Mailing in conjunction with US certified mail, where appropriate. Importantly, the rules caution that postage meter dates, kiosk labels, or other pre-printed postage not affixed by the Postal Service do not serve as proof of timely mailing.