Planning Ahead When Mailing Time Sensitive Documents
Effective December 24, 2025, the United States Postal Service (USPS) adopted final rules that revise how postmarks are defined and treated*. As a result, taxpayers who plan to mail their tax returns and tax payments will need to plan for additional time before any deadlines to ensure timely filing. Taxpayers who do not plan for the updated requirements may face an increased risk that their time sensitive document(s) will be treated as late filed.
On January 2, 2026, the USPS issued a public statement titled Postmarking Myths and Facts, reiterating that they have not changed postmarking practices. However, their adjustment to its transportation network mean some mail may not reach the processing facility on the same day the mail is collected or dropped off. This means, the postmark date applied at a processing center may differ from the actual date the customer mailed the item.
Postal customers will have to mitigate their mail practices (see below) to ensure their mailed item has the desired postmark and/or arrival date. The significance for tax filings is that the Internal Revenue Code Section 7502(a) provides that the postmark date is treated as the date a tax return or payment is delivered to the Internal Revenue Service (IRS),sometimes known as the “mailbox rule”. Taxpayers have long assumed that mailing a return at the post office ensures that same day’s postmark, but with USPS’ Final Rule’s clarification make clear this is NOT always true. It is more likely that mailpieces will likely receive a postmark date later than the date they were deposited at the mailbox.
To mitigate any potential impacts from USPS’ “Final Rule”
Mailing earlier and not being impacted if the item is not processed on the same day
Requesting a manual postmark from a USPS retail employee at the time of filing
Requesting a postage validation imprint label to document the date the mailpiece was received by USPS
Purchase a Certificate of Mailing to document the date the mailpiece was received by USPS
Using USPS Registered Mail or USPS Certified Mail with return receipt requested
Using an IRS-designated private delivery service, which provides its own proof-f-mailing documentation
*USPS Section 608.11, “Postmarks and Postal Possession” (the Final Rule)
(https://www.federalregister.gov/documents/2025/11/24/2025-20740/postmarks-and-postal-possession)
Any accounting, business, Medicare or tax advice contained in this communication, including attachments and enclosures, is not intended as a thorough, in-depth analysis of specific issues, nor a substitute for a formal opinion, nor is it sufficient to avoid tax-related penalties. If desired, we would be pleased to perform the requisite research and provide you with a detailed written analysis. Such an engagement is the subject of a separate engagement letter that would define the scope and limits of the desired consultation services.