The Postal Service added a new section (DMM 608.11) to the Domestic Mail Manual that formally defines the postmark for the first time in a regulation and explains what information it does and doesn’t convey. It took effect December 24, 2025.
A postmark confirms USPS had possession of a mailpiece on the stamped date, but the postmark date does not necessarily match the date USPS first received the mailpiece. Most postmarks are applied by automated machines at processing facilities, and the date reflects when the mail was processed at that facility – not when it was initially deposited. This discrepancy has grown more common under USPS’s Regional Transportation Optimization (RTO) initiative, which adds flexibility between collection and processing schedules.
This is a significant practical problem with perhaps significant legal consequences, even though USPS insists the rule is “just clarification.” For example Internal Revenue Code § 7502, also known as the “mailbox rule.” IRC § 7502 says that if a tax return or payment arrives at the IRS after the deadline, it’s still considered timely if the USPS postmark date is on or before the due date. Courts interpret this strictly – the postmark date controls, regardless of when the taxpayer actually deposited the document.
The problem is that § 7502 and its regulations never actually defined “postmark.” As a result, the USPS’s new DMM 608.11 effectively supplies the operative definition for § 7502 purposes. And that definition now makes clear that a machine-applied postmark reflects the date of first automated processing at a regional facility – not when you dropped it in the mailbox or handed it to a postal carrier. Tax professionals have been calling for the IRS to address this, but nothing had been issued as of the most recent reporting.
And it’s just now getting attention from employment and benefits lawyers. Here’s how the new postmark rule ripples into employer notice obligations. Under federal laws like ERISA, COBRA, HIPAA, and the ACA, employers are required to send a variety of notices to employees concerning health insurance coverage, retirement benefits, and other employee benefits.
Some key examples of these deadlines:
– – General COBRA notices must be sent to new plan participants within 90 days of health coverage starting. COBRA election notices must be sent within 14 days after an employer notifies the plan administrator about a qualifying event, such as a layoff, discharge, divorce, or reduction in hours.
– – Health plans must send HIPAA notices of privacy practices to enrollees within 60 days of any substantial change.
– – HIPAA-covered entities must notify affected individuals without unreasonable delay, or no later than 60 calendar days after discovering a security breach.
– – Other ERISA-required communications include summary plan descriptions (SPDs), summaries of benefits and coverage (SBCs), formulary notices, and annual disclosures – all with their own timing requirements.
– – COBRA regulations specifically say that the initial notice, election notice, and notice of unavailability are considered “provided” on the date they are postmarked. So if the postmark date is delayed by a day or two at a regional processing center, a notice that was mailed on time could be deemed late
Some options to avoid this problem include requesting a free manual (local) postmark at any Post Office retail counter. This stamp will align with the date the customer hands over the mail. Registered Mail and Certified Mail also provide mailing receipts.
The Postal Service claims this rule does not change any actual postmarking operations or procedures. USPS says it’s purely an educational/transparency measure codifying longstanding practices. The era of dropping a deadline-sensitive document in a blue mailbox on the last day and trusting the postmark is effectively over. It would be wise for employers to take affirmative steps to secure proof of the actual mailing date.