The U.S. Postal Service is rolling out changes to its postmark process in 2026 that could affect deadlines for taxpayers, mail-in voting, bill payers and others who rely on postmark dates to avoid late fees and penalties.
A postmark is the official USPS stamp showing where and when mail was accepted. Previously, it reflected the date an item was dropped into a mailbox or handed over at a post office counter.
Under a new rule that took effect Dec. 24, 2025, postmarks on mail deposited in blue collection boxes or neighborhood mailboxes will instead show the date an envelope is first processed by an automated sorting machine — which may be days after it was mailed. The postmark will be applied at regional sorting facilities, not at the time of drop-off.
The change could affect time-sensitive items such as tax returns, charitable contributions, legal filings, mail-in ballots in states where postmarks determine eligibility, rent payments and other bills that use postmark dates to determine whether they were submitted on time.
USPS advises customers to mail important documents several days ahead of deadlines or bring items inside a post office and request a hand-stamped postmark reflecting the date of mailing.
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