Reposted from the CAMICO News release, February 20, 2026 news article.
Recent changes implemented by the United States Postal Service (“USPS”) may affect the postmark dates applied to mailed tax returns, payments, and other time-sensitive correspondence.
Effective December 24, 2025, USPS adopted a final rule adding Section 608.11 to the Domestic Mail Manual regarding USPS postmarks. Machine-applied postmarks will generally reflect the date mail is first processed at a regional USPS processing facility, rather than the date an item is deposited at a local post office or mailbox.
As a result of changes in USPS procedures impacting postmark dates, the postmark date on mailed items may be applied days after the item is delivered to USPS. This may cause a return, payment, or other submission that was mailed on or before a statutory deadline to nevertheless receive a postmark dated after the due date.
Because federal and state tax filing deadlines are determined by the postmark date (not the date of deposit), these changes introduce new timing risks for filings and payments submitted by mail across all jurisdictions.
Under current USPS processing procedures, routine mailbox drop-off, including at after-hours post office slots, may no longer reliably produce a same-day postmark.
For additional information refer to the USPS Postmarking Myths and Facts.
Risk Management Considerations
The USPS changes alter a long-standing assumption relied upon by taxpayers and CPA firms — that depositing mail with USPS by the filing deadline will result in a timely postmark. Under the revised processing procedures, this assumption may no longer hold true.
From a risk-management perspective, CPA firms may wish to evaluate whether existing filing-season practices sufficiently address the increased risk of delayed postmarking, particularly for returns, payments, extensions, and elections mailed close to statutory deadlines.
Electronic filing and electronic payment remain the most reliable methods for timely submission and confirmation. If mailing is necessary, you may wish to obtain proof of mailing, such as a manual USPS postmark obtained at a retail counter; Certificate of Mailing; or sending by Certified Mail, Registered Mail, or another IRS-approved delivery service that provides documented proof of mailing date.
Most clients may not be aware of the USPS’s processing changes and may reasonably assume given historical practices that timely drop-off with the USPS ensures timely filing. Late-postmark penalties may be difficult to contest in the absence of documented proof of mailing date.
Proactive Defensive Documentation
CAMICO strongly encourages CPA firms to apprise clients of the recent USPS processing changes and the potential impact on filing deadlines. Providing advance notice may help manage client expectations and mitigate potential disputes if penalties or interest arise due to delayed postmarking.
In addition, firms may want to consider including language related to the USPS postmark processing changes in transmittal letters to clients (e.g., tax return cover letters, extension transmittals, or payment instructions), particularly where returns, payments, or elections are delivered close to statutory deadlines or where clients are responsible for mailing items themselves.
Sample Transmittal Language
Effective December 24, 2025, the United States Postal Service has implemented changes that may affect the postmark date, and that date may now be later than the date an item is dropped in the mail. Because tax deadlines are based on the postmark date, mailing close to a deadline may result in a late postmark. Obtaining proof of mailing, such as a manual USPS postmark obtained at a retail counter; Certificate of Mailing; or sending by Certified Mail, Registered Mail, or another IRS-approved delivery service that provides documented proof of mailing date can help reduce this risk.
CAMICO offers a sample client advisory notice for this purpose. The client notification template is available on the CAMICO Members-Only Site (www.camico.com) in the Alert section of the home page.
CAMICO policyholders with questions should contact the Loss Prevention department by email at [email protected] or call 1.800.652.1772 and ask to speak with a Loss Prevention Specialist. Additional risk management resources are available on CAMICO’s Members-Only Site (www.camico.com).
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