On November 24, 2025, the U.S. Postal Service (“USPS”) finalized a rule regarding when and how postmarks are applied. See 39 C.F.R. § 111 (2025). It is important for taxpayers and their advisors to be aware of the change because it has an impact on proving that a document was filed. While the rule does not change how mail is processed, it does change how postmarks should be understood, especially when deadlines matter.
What Changed?
While postmarks have long been relied upon as evidence that a document was mailed on a certain date, the new rule makes clear that this assumption is not always accurate. In most cases, postmarks are applied by automated machines at regional processing facilities, and not at the local post office where a piece of mail is dropped off. As a result, the date printed on a postmark may reflect the date the piece was first processed—not the date it was actually placed in the mail or collected by the USPS.
Lindabury, McCormick, Estabrook & Cooper, P.C. Firm News & Events


