April 1, 2026

The U.S. Postal Service recently clarified how postmarks work for deadline-sensitive mail. USPS says the wording added to its Domestic Mail Manual on December 24, 2025, did not change how mail is postmarked, but it did clarify that a postmark may reflect either the date a mailpiece was accepted at a retail counter or the date of its first automated processing at a processing facility. As a result, the postmark on a mailed tax document may not always match the date the item was placed in a mailbox or drop box.

Taxpayers who want proof that a mailing was accepted by USPS on a particular date should consider using one of the methods USPS identifies as aligning with the actual acceptance date. A customer may request a manual local postmark at the retail counter of any Post Office, station, or branch at no extra charge. A Postage Validation Imprint (PVI) label printed by a USPS employee at the counter when postage is purchased and the item is handed over also reflects the date USPS accepted the mailpiece. USPS also says customers who want a record of the acceptance date may purchase a Certificate of Mailing; Certified Mail and Registered Mail also provide mailing receipts for individual mailpieces.

By contrast, pre-printed labels from Self-Service Kiosks, Click-N-Ship, and postage meters show only that postage was purchased and the date it was printed. USPS says those labels do not by themselves prove when USPS accepted the mailpiece.

For taxpayers sending time-sensitive IRS documents, it may be prudent to mail early, use a USPS retail counter option that provides evidence of acceptance, or use an IRS-designated private delivery service when appropriate. The IRS says only certain DHL, FedEx, and UPS services qualify for the “timely mailing treated as timely filing/paying” rule, and those services may require a street address rather than a P.O. box.

IRS Private Delivery Services:https://www.irs.gov/filing/private-delivery-services-pds