The United States Postal Service has modernized how postmarks are applied to mail—and this change affects anyone who mails time-sensitive documents, including tax returns, estimated tax payments, voting ballots, and other deadline-driven correspondence.
Under the new system, which took effect December 24, 2025, postmarks no longer reflect the date you drop off your mail in a post office box or even at the post office. Instead, the postmark date is the day your envelope is first processed by an automated USPS sorting machine—which could be one or more days after you mail it. That means if you drop your tax return in a mailbox on April 15, it might not be postmarked until April 16 or later.
This matters because the IRS honors the "timely mailing as timely filing" rule. If your tax return or payment is postmarked by the deadline, you're in compliance—even if the IRS receives it days later. But the new USPS system shifts the date that gets recorded as your postmark, which could create unintended late filings and trigger penalties and interest.
Steps to Ensure Your Filings Are Postmarked on Time
- Mail early whenever possible.
- Request a manual postmark. Visit a USPS retail counter and ask the clerk to hand-stamp your envelope. This free service ensures the postmark reflects the date the USPS accepts your mail.
- Choose certified mail. These services provide documented proof that USPS accepted your filing on a specific date.
- Consider electronic filing and payment. E-file your return and pay electronically for immediate confirmation and peace of mind.
A little planning now can help keep your taxes #LessTaxing later!