New USPS Regulations May Cause Issues for Taxpayers

The US Postal Service (USPS) recently adopted rules in the Domestic Mail Manual (DMM) to redefine postmarks. Effective December 24, 2025, Rule 608.11 of the DMM states that the postmark stamped on a customer’s mailpiece may be applied when it is processed at a regional hub, rather than when it was originally deposited.

US taxpayers who mail their tax return to the IRS still follow the legal standard known as the “mailbox rule.” This ruling under IRC §7502(a)(1) states the date of the US postmark on the cover in which the tax return is mailed shall be deemed the date of delivery. Accordingly, a postmark date confirms USPS possession but may not align with the date the mail was first dropped off. Because mail is increasingly routed through larger regional hubs, the automated postmark date may be later than the date a customer tendered the mail triggering late-filing or late-payment penalties with the IRS. The IRS stated that while their process remains unchanged, the postmark timing issue may occur more frequently, and they are working to better educate the public.

A customer may request a manual postmark at any office, station, or branch to align the postmark date with the date on which the USPS first accepts possession of the mailpiece. A best practice for taxpayers mailing their return is to purchase a Certificate of Mailing, Registered Mail, or Certified Mail receipt as a formal record of the acceptance date, serving as proof of a timely filing for the IRS, state, or local filing agency. Under Treasury regulations, the date on a Certified or Registered Mail receipt is treated as the official postmark date. This is considered the strongest evidence of timely mailing in a dispute with the IRS.

Taxpayers should consider electronically filing, as permitted, to ensure their tax returns are processed accurately and without delay. If a taxpayer must file a paper return, follow these guidelines to ensure you meet the deadline:

• Avoid mailing on the due date: Send  your return early to prevent delays and/or late-filing or late-payment penalties
• Obtain a postmark: If filing near the deadline, hand-deliver your return to a postal clerk and request a physical postmark
• Use Certified Mail: Keep a Certified Mail receipt as legal proof that your return was mailed on time

Have questions about the new USPS rules? We’re here to help. Navigating IRS deadlines is stressful enough without worrying about mail transit times. If you have questions about how these changes affect your filing strategy or need assistance transitioning to electronic filing, reach out to our team today. We’ll help you ensure your returns are documented, submitted, and accepted on time.