How The Postmark Change Impacts Tax Return Filings and Payments

A recent change by the U.S. Postal Service may affect how the IRS treats certain tax documents. Starting December 24, 2025, mail is no longer postmarked when you drop it off. Instead, it is postmarked later, after processing at a regional mail facility.

Why Postmarks Matter on Your Tax Return

The IRS treats a mailed tax return or payment as on time if it has a postmark dated on or before the due date. This is part of the longstanding “mailbox rule” under IRC Section 7502.

With the new USPS rule taking effect on December 24, 2025, the postmark may not match what you actually handed to the Postal Service. Instead, it may reflect a later date when it was first processed by sorting machines.

This could lead to problems such as:

• A tax return or tax payment is being treated as filed or paid late,
• Interest or penalties because the IRS sees a late postmark, or
• Extra time spent proving you mailed it on time.

How to Protect Yourself When Mailing Tax Documents or Payments

If you must mail something to the IRS, here are ways to make sure you have strong proof of when you mailed it:

Go to the Post Office Counter

• Ask for a manual hand-stamped postmark that shows when you handed it over.
• Buy your postage at the counter so the imprint shows the correct acceptance date.

Use Certified or Registered Mail

• These options give you a dated receipt.
• This receipt can help show the IRS when you mailed your forms.

File or Submit Electronically

• E-filing or online payment has a built-in timestamp.
• Electronic filing eliminates uncertainty about postmarks.

Charitable Giving Impact

While the focus here is on tax return and tax payment timing, this postmark change also affects year-end charitable deductions. Under IRS rules, a mailed donation is considered a charitable contribution in the year shown by the postmark.  But because postmarks may now be applied later, a gift sent on Dec. 31 could be postmarked in January and count for the next tax year instead.

To protect your deduction, consider:

• Asking for a hand-stamped postmark
• Using certified mail or an in-office postmark

What This Means for You

The bottom line is that even something as simple as mailing a tax return or payment could now carry a greater risk of an unintended late date stamp. If you anticipate mailing time-sensitive tax documents, take one of the extra steps above to protect your filing deadline.

If you have questions about how this change might affect your specific tax situation or to ensure you meet tax deadlines, reach out to your tax advisor at Isdaner & Company before sending anything by mail to the IRS.