USPS Clarifies Postmark Rule: What Employers and Employees Need to Know

Effective December 24, 2025, the U.S. Postal Service (USPS) implemented a change to how postmark dates are assigned. The rule located in the “Postmarks and Postal Possession” in the Domestic Mail Manual clarifies that the official USPS postmark date is not the date a mail piece is dropped off, but the date it is first processed by an automated USPS sorting facility.

This clarifying change can have significant implications for employers, plan sponsors, and employees who rely on mail service to meet legal deadlines.

USPS Postmark Date

According to the USPS, the postmark date represents when USPS automation equipment first processes the mail item and not when:

• The item is handed to a postal clerk
• Dropped at a local post office
• Placed in a blue collection box
• Placed in a residential or business mailbox

Because mail is now routed from local offices to regional processing centers, several days may pass between drop off and the automated postmark. Individuals or business that rely on the mailing date, the USPS encourages customers to visit a post office location to receive a manual postmark date so that the date matches the date of mailing.

Implications for Employees and Employers

Many federal and state compliance deadlines rely on a timely postmark, including:

• Tax filings, payments, and extensions (e.g., Forms 1095, ESRP responses, PCOR filings, etc.)
• ERISA and health plan notices (e.g., HIPAA special enrollment requests, SPDs, SARs, SMMs, etc.)
• COBRA notices
• Claims and appeals submissions
• Leave or disability notices (e.g., FMLA, state mandated leave, medical certifications, etc.)
• FSA/HRA substantiation or reimbursement claims
• Other regulatory filings or contractual notices requiring “mailed by” documentation

If the postmark occurs after a statutory deadline even when the employee or the employer mailed the item on time, it may be considered late. Employees that miss delivery deadlines can result in lost appeal rights, denied reimbursements, and denied or termed benefits. Employers may face excise tax or penalty violations under the Internal Revenue Code and civil penalties under ERISA.

Employer Action

Employers should consider the following to ensure timely mail-in delivery:

• Update internal mailing procedures by requiring time sensitive documents be mailed using methods that provide verified mailing dates (e.g., manual postmark, certified mail, proof of mailing).
• Discuss with carriers, TPAs/stop loss providers, COBRA administrators, and Payroll or tax vendors to confirm any changes to mail-in requirements.
• Encourage employees to use verified mailing options and update plan communications (e.g., SPD, claims/appeals procedures).
• Use electronic delivery whenever permitted to ensure plan notices are delivered timely.