How the Mailbox Rule Works
For decades, the U.S. government has operated under Internal Revenue Code (IRC) Section 7502 regarding mailing deadlines for official documents. Commonly referred to as “the mailbox rule,” this rule states that the U.S. postmark date on a properly mailed tax return, statement, claim, or payment is considered the postmark date, as long as the mail item is properly addressed, has sufficient postage, and is deposited in a U.S. mailbox.
For decades, taxpayers have relied on the postmark date matching the mailing date. However, that precedent is changing due to a recent change in the United States Postal Service’s (USPS’s) processing rules.
What Has Changed With USPS Postmarks
According to the USPS, most postmarks are applied at processing centers, not at drop-off locations. Because of this, postmarks reflect the date a mail piece is processed, which isn’t always the same date it was deposited by the sender. The USPS’s new guidance has been updated to reflect this reality and notify taxpayers that the postmark date may be later than the day the mail was accepted by the USPS.
This change in policy was published in the Federal Register on November 24, 2025, and became effective on December 24, 2025, which means it will impact 2025 tax filing deadlines.
How to Manage the Change
Taxpayers can no longer be confident that a mailpiece deposited in a mailbox on April 15 will be postmarked that day. This means a tax return mailed on April 15 could be postmarked on April 16 or later, and the IRS would view it as a late filing.
The following are several suggestions to help ensure your tax return is compliant with filing deadlines.
File electronically whenever possible
The best way to avoid mailing delays is to file your return and make necessary payments electronically. In addition to providing proof of filing, the benefits of e-filing include faster refunds, increased accuracy, enhanced privacy protection, and the option to streamline both federal and state returns through a single software program.
Purchase postage at a retail counter
Purchasing postage at a retail counter ensures the postage validation imprint (PVI) stamped on the mail piece reflects the date of acceptance.
Request a manual postmark
Upon specific request, the USPS will provide a manual postmark at no additional charge. Because the manual postmark is stamped on receipt of the mail piece, the date of the stamp is consistent with the drop-off date.
Purchase a certificate of mailing or use certified/registered mail
A certificate of mailing serves as proof of the date on which the USPS accepted a piece of mail. Sending a mail piece by certified or registered mail also provides a mailing receipt that can be used to prove compliance with tax filing deadlines.
This information is not intended to be a substitute for specific individualized tax advice. We suggest that you discuss your specific tax issues with a qualified tax advisor.