USPS Postmark Rule Could Impact Timely Filing of Mailed Documents

Under a new U.S. Postal Service (USPS) rule effective December 24, 2025, the USPS has clarified that a machine-applied postmark indicates the date the item is first processed by USPS using an automated sorting machine, which may be later than the day it was received by the post office. That means a document received by the post office on time could end up with a postmark dated after the deadline.