A recent update from the U.S. Postal Service (USPS) could impact how the IRS determines whether certain tax filings and payments are considered timely.
Beginning December 24, 2025, mail is no longer postmarked when it is dropped off. Instead, the postmark reflects when the item is first processed at a USPS sorting facility. While this may seem like a small operational change, it can create complications for taxpayers who rely on mailing documents close to IRS deadlines.
As noted by J.D. Supra, deadlines matter because the IRS typically relies on the postmark date, not the date a document was placed in the mail, when determining whether something was filed on time.
Why Postmarks Matter for Tax Filings
Under long-standing tax rules, a mailed return or payment is treated as timely if it carries a postmark dated on or before the filing deadline. This approach, often referred to as the “mailbox rule,” has been a standard part of tax administration for decades.
With the new USPS process, however, the postmark date may no longer align with the date you mailed your documents. Instead, it may reflect a later processing date, which can lead to unintended consequences.
View the Before vs. After the Postmark Change Hypothetical Taxpayer Scenario to see how this works.
Potential issues include:
- A tax return or payment being treated as late.
- Interest or penalties assessed due to a later postmark date, and/or
- Additional time and documentation are required to demonstrate timely mailing.
Steps to Reduce Risk When Mailing Tax Documents
If mailing tax-related items is necessary, taking a few extra precautions can help protect against postmarking issues.
- Visit the Post Office Counter
- Request a hand-stamped postmark showing the date the item was accepted.
- Purchase postage at the counter so the acceptance date is clearly documented.
- Use Certified or Registered Mail: These options provide a dated receipt that can serve as supporting documentation if questions arise.
- File or Pay Electronically When Possible
- Electronic submissions include a clear timestamp.
- E-filing and online payments remove uncertainty around postmarks entirely.
A Note on Charitable Contributions
This change may also affect year-end charitable deductions. For tax purposes, a mailed charitable contribution is generally deductible in the year indicated by the postmark. If a donation mailed on December 31 is processed and postmarked in January, it may be treated as a contribution for the following tax year.
To help preserve the intended deduction timing, consider:
- Requesting a hand-stamped postmark
- Using certified mail or similar services
What This Means Going Forward
The key takeaway is that mailing tax documents at the last minute now carries more risk than it did in the past. A delay between drop-off and processing could result in a postmark dated after the filing deadline, even if you acted on time.
If you expect to mail time-sensitive tax documents, planning or using one of the safeguards above can help reduce exposure to penalties, interest, or IRS notices.
If you would like to discuss this or any other accounting matters, we’d be happy to help. Please reach us at 646-849-4267 or contact us.