On November 24, 2025, the United States Postal Service (USPS) issued a final rule regarding postmarks and postal possession. Although its primary purpose is to clarify operational issues for postal customers, the final rule carries very real compliance implications for sponsors and service providers of both defined benefit (DB) and defined contribution (DC) retirement plans. The final rule notes that the new language does not change any current postal procedures or postmarking methods—its purpose is simply to enhance public understanding of postmarks and how they relate to the mailing date.

The final rule went into effect on December 24, 2025.

In this article we explain why postmarks matter to retirement plans, clarifications in the final rule, and what plan administrative changes may be needed to ensure mail is timely postmarked, and we list the operational items plan sponsors and their advisors may need to review and potentially adjust going forward.

Why postmarks matter to retirement plans

Under ERISA and the Internal Revenue Code, numerous deadlines can be satisfied by “timely mailing,” meaning the form, submission, or document is considered filed or provided on time if it is mailed by the deadline, regardless of the actual delivery or receipt date, as long as there is proof it was mailed on time. Although use of electronic filing and delivery methods by retirement plans are now prevalent, e.g., for certain government forms for which electronic filing is mandatory or delivery of participant notices and disclosures for which electronic delivery is optional, physical mailings still occur. Common examples include:

• Notices sent to participants, including but not limited to:
• DC plans: safe-harbor, automatic enrollment, qualified default investment alternative (QDIA), fee disclosure, blackout periods, summary annual report, quarterly benefit statements, summary plan description, summary of material modifications
• DB plans: annual funding notice, summary plan description, summary of material modifications
• Rollover checks mailed to the trustee
• Participant elections upon benefit commencement
• Certain government filings that may be filed by mail, including but not limited to:
• Form W-2 (if not required to e-file) – sent to the Social Security Administration, to state or local governments, and to employees to report wages earned and taxes withheld
• Form 5558 – sent to the IRS to extend the Form 5500 or Form 8955-SSA
• Form 15315 – sent to the IRS to annually certify the status of a multiemployer DB plan¹

Plan administrators generally rely on the presence of a USPS postmark to document “proof of mailing.” Treasury regulation 301.7502-1(c)(1)(iii)(a) provides that a mailing is considered timely filed if the postmark on the envelope or package is made by the United States Postal Service and shows a date on or before the prescribed deadline for the filing. If the postmark is not legible, the filer must prove when it was made. Also, if a document with a timely postmark arrives later than expected, the sender may need to show it was mailed on time.

This new final rule clarifies when, where, and how postmarks are applied and the potential lag between USPS’s possession of a mail piece and the date that appears on the envelope.

Clarifications made by USPS

Definition of a postmark

The final rule clarifies that a postmark is the marking applied to a piece of mail, and if applicable, it cancels the postage to prevent its reuse. When done at a retail location, the postmark shows the name or location of that retail unit and the date the mail was accepted there. If applied at a processing facility, it indicates the facility’s name or location and the date the mail went through its first automated processing.

Potential lag between USPS possession and the postmark date

Most postmarks continue to be applied at processing facilities, not at the local post office or retail counter, meaning the postmark date may lag the handoff date by one or more days. This lag may happen more often as the USPS implements its Regional Transportation Optimization (RTO) operational efficiency improvement initiative, which will streamline mail operations by centralizing mail collection and processing at regional hubs. Mail collected at local post offices or collection boxes far from a regional hub may not be postmarked until it arrives at the hub, which could be one or more days later.

The postmark for any mail deposited in a blue collection box, at an Approved Postal Provider location, or via an authorized pickup will be applied when the piece reaches a processing center.

Auxiliary markings and data

Throughout postal processing, USPS may add markings to mail or generate scan data. These auxiliary markings and data show that USPS has handled the mail, but they do not serve as proof of the date when the USPS first accepted and had possession of the mail. Additionally, the absence of such markings or data does not mean USPS did not accept the item. Examples of auxiliary markings and data include:

• Identification tags: Mail processed on automated equipment often receives a fluorescent tag, which encodes details such as the date the tag was applied.
• Intelligent Mail® barcode (IMb) scans: Customers add IMbs to mail, which contain information like the mailer’s identity, requested services, serial numbers, and routing codes. While the pre-mailing, customer-applied IMb itself does not confirm USPS possession of the mail, IMb scan events throughout processing record the time and location of each scan. Commercial mailers can track mail using IMb scan data through the Informed Visibility interface. For accuracy, IMbs must be properly prepared using USPS’s formal standards for IMbs; duplicate or illegible barcodes can affect data reliability.

Postmarks aligning with the date USPS accepts possession

Mailers who need their items postmarked by a specific date can use one of the following options to ensure the postmark meets their requirements:

• Mail the item sooner. Mailers can send their time-sensitive mail well before the deadline to achieve the desired postmark date, at no additional cost.
• Request a manual postmark. A manual postmark will align with the date the local USPS location first accepts possession of the mail. These postmarks are provided at no cost upon request at the retail counter of any post office or other USPS station or branch. However, customers intending to submit a large quantity of mail—50 or more pieces—for local postmarking should reach out to the postmaster or another manager ahead of time to confirm that sufficient resources will be available.
• Obtain a Postage Validation Imprint (PVI) label. These labels are printed and applied to mail by USPS at retail locations when the mail is first accepted. They show the amount of postage paid and, similar to manual (local) postmarks, include the name of the retail unit and the date the mail was accepted there.
• Purchase a mailing receipt. Mailers seeking proof of when USPS first accepted their mail can purchase a Certificate of Mailing, which gives them a receipt evidencing the date their mail was handed over to USPS for mailing. Certified Mail, Registered Mail, and Priority Mail Express also include mailing receipts for individual items.

Please note that preprinted labels applied by the sender before mailing—such as those from Self-Service Kiosks (SSK), Click-N-Ship, or postage meters—only indicate that postage was purchased and the date it was printed. These labels do not confirm that USPS accepted the mail or specify the date it was accepted.

Operational items to review

Plan administrators should map every operational and compliance deadline that relies on postmarks as the date sent and identify safer evidence methods. Milliman’s annual calendars of key administrative dates² may help with this review.

• Reexamine “timely mailing” procedures. Review the plan’s documented procedures to make sure timely mailing language is clear. USPS acknowledges occasional mistakes can occur, e.g., the postmark is not applied (due to two pieces of mail being stuck together), or the postmark is illegible. Plan procedures should describe how such instances will be handled.
• Update participant communications. While electronic participant communications and elections are increasingly more commonplace, handwritten elections and physical mailings still occur. In such instances, plans should update forms, election packages, and required notices to instruct participants on the safest means of mailing time-sensitive items. Encourage use of Certified Mail, Certificates of Mailing, USPS tracking scans, or comparable private delivery service documentation or provide business-reply envelopes that include bar-coded PVIs applied at the counter. For mass mailings of required notices, instruct print vendors to request PVIs or use IMbs and to supply daily acceptance-scan data for your permanent plan compliance files.
• Allow extra time for mailing or transition to electronic transmission and distribution methods. Plan procedures that may involve physical mailing should be reviewed to build in additional mailing lead time where necessary or transition to electronic methods. For example, procedures for making contributions intended to satisfy minimum funding for pension plans or excise-tax payment deadlines should be reviewed. Plan sponsors that are still mailing checks to the plan’s trust for contributions and other remittances should transition to electronic funds transfer (EFT) or overnight tracked delivery and encourage EFT delivery for participant rollover checks. For plans that are not utilizing electronic delivery for participant notices and disclosures, plan sponsors and administrators should work with their plan service providers to explore and implement its use following federal rules and guidance issued by the Department of Labor for ERISA-required disclosures and the Treasury and IRS for IRS-required notices.

Looking ahead

While the USPS’s final rule does not change ERISA or the Internal Revenue Code requirements, it underscores the importance for plan sponsors, plan administrators, and service providers to proactively review and update their mailing procedures to ensure continued compliance and minimize the risk of missed deadlines.

Please contact your Milliman consultant with any questions or assistance with procedural updates or participant communications that align with the updated USPS framework.

¹ Due to a glitch in the mobile-friendly forms webpage, the Form 15315 may be mailed, faxed, or emailed to the IRS. See more details at https://www.irs.gov/retirement-plans/employee-plans-news.

² Milliman annually publishes three separate calendars of key administrative dates, one each for single-employer DB, multiemployer DB, and DC plans.