The U.S. Postal Service (USPS) recently published a final rule regarding postmarks and postal possession that entered into effect on December 24, 2025. The new rule defines postmarks, identifies markings that qualify as postmarks, describes the circumstances of the markings’ application, and indicates how customers can obtain evidence of USPS mailing.
The summary section of the rule notes that the new provisions do not reflect a change in existing practices but are intended to improve the public’s understanding of postmarks and their relationship to the date of mailing.
The new postal rule clarifies that the USPS will generally postmark mail on the day received in the distribution center or retail unit, which may not be the same day when the piece of mail was originally submitted or tendered for mailing. The rule states: “…while the presence of a postmark on a mailpiece confirms that the Postal Service was in possession of the mailpiece on the date of the postmark’s inscription, the postmark date does not inherently or necessarily align with the date on which the Postal Service first accepted possession of the mailpiece.”
A common provision that taxpayers often rely on for paper tax returns and payments is the timely mailing/payment rule under Section 7502 (commonly referred to as the “mailbox rule”). Under this rule, a return or payment may be deemed timely filed if it was postmarked by the due date, properly addressed, and delivered. If a tax return or payment meets those requirements, it will be deemed filed on the mailing date (postmark date), even if delivered after the due date.
The new postal rule provides that customers who want proof of mailing as of the date the piece of mail was originally submitted can request a manual (local) postmark at the Post Office and discusses obtaining proof of mailing (for example, a Certified Mail receipt) to demonstrate when the Postal Service accepted possession. The new rule also cautions that pre-printed labels “… show merely that a customer has purchased postage and the date on which the postage was printed; they do not in themselves demonstrate that the Postal Service accepted the mailpiece, or the date on which any such acceptance occurred.”
BDO Insight
Evidence of timely mailing or filing is a crucial part of the federal tax filing system and that of U.S. states and localities. The new USPS rule indicates that there could be delays in the postmarking of a mailed document, including tax returns or payments, depending on the method of submission. Taxpayers seeking to utilize the mailbox rule as proof of timely submission are urged to consider this potential additional time and to request a manual postmark at a local U.S. post office location. Taxpayers may also consider utilizing specifically identified private delivery services that meet the requirements under Section 7502.
Please visit BDO’s Corporate Tax Services page for more information on how BDO can help.