Tax Alert: Mailings to IRS Impacted by New USPS Postmark Process
If you typically use the mail to submit your tax return, file extension requests, or make payments of tax estimates and balances, be aware that effective December 24, 2025, the U.S. Postal Service (USPS) has changed their official USPS postmark process. This change may significantly impact how time-sensitive documents such as tax returns and bill payments are legally considered “sent” to the IRS.
Previously, the USPS postmarked mail on the date it was deposited in a mailbox. Under the new rule, the postmark will reflect the date the envelope is processed by an automated USPS sorting machine at a regional processing center. This could potentially be days after it was first dropped off.
The “mailbox rule” is a statutory provision in the tax code (IRC Section 7502) whereby the IRS accepts tax returns and payments mailed by the due date as timely filed, even if the documents are physically received and processed after the due date. The official USPS postmark has been upheld as proof of timely submitted filings and payments via this rule in disputes with the IRS. While the “mailbox rule” continues to apply, the date of official USPS postmark will now change.
Under the new process, tax returns or payments dropped in a USPS mailbox on April 15th, the IRS tax filing deadline for individuals, may no longer reflect April 15th as the official postmark date. This change has the potential to trigger late filing or late payment penalties with the IRS for Taxpayers who are unaware of the new process.
In summary, the “mailbox rule” still applies in determining when paper filings and payments are deemed sent to the IRS. While this change may appear technical, it has meaningful implications for taxpayers who send tax returns or payments by mail. To avoid unintended late filings or payments, we strongly recommend that all paper-filed tax returns and payments be sent via certified mail and presented at the post office counter to obtain a manual USPS postmark. Certified mail receipts and return receipt postcards should be retained for your records, as they serve as critical evidence of timely mailing in the event of a dispute with a taxing jurisdiction.
