Final US Postal Service Rules on Postmarks May Complicate Taxpayer Filings for Some Filers

Recently finalized rules from the United States Postal Service seek to clarify that the date on a postmark does not “necessarily represent either the place at which, or the date on which, the Postal Service first accepted possession of the mailpiece” and may in fact be applied to a piece of mail after the date the mailpiece was placed in the possession of USPS. For taxpayers hoping to rely on the “timely mailed is timely filed” ruling when filing tax returns or other documents or submitting tax payments, there are avenues for filing to help avoid risk.

Effective December 24, 2025, the USPS adopted final Section 608.11, Postmarks and Postal Possession (the Final Rule), as part of the Domestic Mail Manual. [1]

Section 608.11.3 of the Final Rule states that “[t]he presence of a postmark confirms that the Postal Service accepted custody of a mailpiece, and that the mailpiece was in the possession of the Postal Service on the identified date. However . . . the postmark date does not necessarily indicate the first day that the Postal Service had possession of the mailpiece.” (Emphasis added.) Rather, the postmark date “shows the date of the first automated processing operation performed on a mailpiece or, alternately, the date when a mailpiece was accepted at a retail unit.”

The USPS clarified, however, that the Final Rule was not intended to “change any existing postal operations or postmarking practices, but [was] instead intended to improve public understanding of postmarks and their relationship to the date of mailing.”

In response to comments to the Proposed Rule about agencies, including the Internal Revenue Service, relying on postmark dates to determine timeliness, the USPS noted that “postmarks applied at originating processing facilities have never provided a perfectly reliable indicator of the date on which the Postal Service first accepted possession of a mailpiece, and this fact will become more common under RTO [Regional Transportation Optimization]. Therefore, to the extent that customers currently have this view of the postmark, it does not reflect the realities of postal operations.” (Emphasis added.)

Instead, the USPS believes that the Final Rule serves to “make the actual meaning of the postmark more widely known, so that customers who may currently lack a clear understanding of the postmark can, if necessary, make adjustments to their mailing behavior—for example, by dispatching their mailings earlier, obtaining a manual (local) postmark at a retail location at no additional cost, or purchasing a Certificate of Mailing.”

Significantly, in the preamble to the Proposed Rule the USPS stated that it believes the upcoming implementation of the RTO will lead to transportation changes that would increase the likelihood that mailpieces will not arrive at Postal Service processing facilities on the same day that they were initially accepted by the Postal Service. This means that the date on the postmarks applied at the processing facilities will not necessarily match the date on which the customer’s mailpiece was collected by a letter carrier or dropped off at a retail location.

APPLICATION TO TAX FILINGS

In general, taxpayers may timely submit any required return or other document either by timely filing it with the IRS or by timely mailing the return. Under Internal Revenue Code Section 7502(a)(1), “[i]f any return, claim, statement, or other document required to be filed, or payment required to be made, . . . is delivered by the United States mail to the agency, officer or office . . . the date of the United States postmark stamped on the cover . . . shall be deemed to be the date of delivery or date of payment.” (Emphasis added.)

In practice, taxpayers have generally interpreted this to mean that a filing, payment, or other document will be considered to have been timely filed if is it submitted to the USPS ahead of the pickup time or facility closing time where the taxpayer mails the document. The logic for this approach, under Section 7502, relied on the assumption that the postmark applied to the filing will reflect the date on which the USPS took possession of the document.

As noted above, however, the Final Rule clarifies that the date a postmark is applied to a piece of mail may not necessarily correspond with the date that the mail was physically delivered to the USPS, may well be applied after that date, and the USPS expects that the “gap” between the date of physical delivery and date of a postmark will increase due to anticipated changes to USPS procedures under the RTO.

While, as aforementioned, the USPS indicated that the Final Rule was not intended to represent a change to existing postal practices, the practical consequence of an increasing number of cases where the postmark shows a date after the date of physical mailing by the taxpayer, along with clear regulations “clarifying” that the date of a postmark is not necessarily the date of physical mailing by the taxpayer, is clear: simply submitting a mailing to the USPS ahead of the pickup time or relevant facility closing time should not be relied upon to constitute “timely filing” of the document.

Absent some significant change in USPS operations, taxpayers filing tax returns and other tax documents by traditional first-class mail, and to which a filing deadline applies, should adjust by mailing the document earlier, requesting and obtaining a manual postmark at a retail counter at the time of mailing, and/or obtaining a certificate of mailing at such time. Failing to do so runs the risk that a return, payment, or other document that is timely turned over to USPS will be postmarked after the filing or due date, with associated and sometimes significant financial consequences.

As a best practice, taxpayers who physically mail documents to the IRS or Tax Court should send the documents via certified mail with return receipt requested or ship the documents using a designated private delivery service (PDS). 26 CFR § 301.7502-1(c)(2) explains that if a document or payment is sent by certified mail “the date of the U.S. postmark on the [certified mail] receipt is treated as the postmark date of the document or payment.” This simple step helps eliminate the risk of a postmark on an envelope that does not correspond to the date it was provided to USPS.

The Treasury regulations [2] also explain that the date of delivery to the PDS, as recorded in the PDS’s electronic database, is equivalent to proof of registered or certified mailing. [3]