Consequences Regarding USPS Postmark and Mailing Practices for IRS Mailing

By: Matthew E. Foreman, Megan E. Wilson, and Bristol Francis

Introduction

Effective December 24, 2025, the United States Postal Service (“USPS”) amended the Domestic Mail Manual (the “D.M.M.”) by introducing section 608.11, Postmarks and Postal Possession.¹ While the amendment does not substantively change current practices, the amendment clarifies postmarking and mailing practices already in existence by bolstering the public’s understanding of postmarks and rules governing the deemed postmark date of mailed items.

While this amendment affects many people, it is of specific importance to taxpayers and their advisors. Taxpayers who are obligated to deliver items to the Internal Revenue Service (the “IRS”) and who do so through the USPS should utilize the clarity in the D.M.M. to ensure that the deemed date of the mail item falls within the prescribed period of mailing the item, whether in the Internal Revenue Code (the “I.R.C.” or the “Code”), Treasury Regulations (the “Regulations”), or any sub-regulatory guidance such as the Internal Revenue Manual (the “I.R.M”).

The Mailbox Rule for Tax Purposes

The Mailbox Rule originated in contract law,² where an act (acceptance of a contract, filing of a document, etc.), is considered effective when it is placed in the mail, not when it is received by the offeror. For federal purposes, or if the IRS is the recipient, the common law mailbox rule has historically applied: the filing of a tax return or other document is effective upon proper dispatch by mail, and this creates a presumption of timely filing even if the mailed item is delayed or not received by the government.³ In the context of tax, the Mailbox Rule helps to determine the date that a document or payment is deemed to have been filed with IRS.

The Code provides that filings or payments that are mailed via USPS are deemed to be filed or paid on the date of the postmark stamped on the envelope.⁴ The postmark date is defined as the date of the postmark stamped on the cover of the mailed item, which follows the postmark rules issued by the USPS.⁵ For the IRS to consider the filing or payment to be timely, the item’s postmark must be on or before the IRS’s prescribed final due date. However, if the item’s postmark date is after the date proscribed in the Code, Regulations, or otherwise, the filing will not be considered timely, and will therefore lead to missing a deadline or the imposition of interest and penalties.⁶

Generally, the taxpayer assumes the risk of the postmark date and bears the burden of proving the mail was delivered within the prescribed window. However, taxpayers can mitigate this risk by sending mail via USPS through certified mail and getting a timely postmark on the item.⁷ If a delivery service other than the USPS is used and the postmark date is timely, the taxpayer must prove (i) the payment was actually deposited in the U.S. mail before the prescribed day and the date of the postmark, (ii) delay existed, and (iii) the cause of the delay.⁸

Domestic Mail Manual Section 608.11

The amendments to the D.M.M. clarify the USPS’s postmark and mailing rules. The D.M.M. provides instructions in an attempt to align the postmark date with the date of the USPS’s actual possession of the mailed item by explaining how the postmark date is issued depending upon certain events. The D.M.M. explicitly states that the postmark date is the date the USPS is in possession of and has accepted the mailed item, and not necessarily the first day the USPS is merely in possession.⁹ For example, if the customer wants to mail an item via USPS and goes to USPS on a Friday, the USPS will place the postmark on the date the USPS deems that is has accepted and also taken possession of the mailed item. Depending on certain conditions addressed in the D.M.M., the USPS may issue a postmark date that is later than Friday, the day the customer brought the mailed item to the USPS and paid for it. This is due to a possible discrepancy between mere possession and actual acceptance.

Section 608.11.1 of the D.M.M. defines a postmark as a “marking applied by the postal service to a mailpiece.” If the marking is applied at a retail unit, or a local Post Office retail counter by a Post Office employee, the postmark will display the date on which the mailed item was accepted at the retail unit. If the marking is applied in a processing facility, or the taxpayer did not opt for application at a retail unit, then the postmark will display the date of the first automated processing operation executed on the mailed item. This date may not be the anticipated postmark date because the date inscribed by a postmark at a processing facility “may be later than the date that mailpiece was first accepted” by the USPS instead aligning with the processing date.¹⁰

To ensure alignment between the intended postmark date and the date on which the USPS first accepted possession of their mailpiece, customers may request a local postmark at the retail USPS store that will serve as the postmark date as if it were being processed through a processing facility.¹¹ For proof of postal acceptance, customers may purchase a Certificate of Mailing.¹²

Recommendations for Taxpayers

Taxpayers responsible for timely filing income tax returns or a claim for a refund should heed section 7502 of the Code and the USPS’s postmark practices. If the IRS requires a taxpayer to deliver certain items, the taxpayer should either (1) wait in the retail line for a USPS employee to issue a postmark date or (2) if a postmark will be issued by a processing facility, request a local postmark for no additional fee on the day the taxpayer delivers the mailed item. Regardless of which option the taxpayer chooses, the taxpayer should also purchase certified mail with the intended postmark date as proof to the IRS.

In both scenarios, the D.M.M. indicates that the USPS’s acceptance of the mailed item will align with the intended postmark date.

Conclusion

It’s critical that taxpayers follow the D.M.M. rules and taxation practices to avoid penalties for failure to mail items to the IRS in a timely manner. If the IRS has prescribed a date for you to mail a specific item, whether through USPS or not, your postmark date may not align with your intended postmark date if you do not follow specific steps.

For guidance on potential deductions or other tax-related matters, contact FRB’s Taxation Practice Group at (212) 203-3255 or fill out the form below.

DISCLAIMER: This summary is not legal advice and does not create any attorney-client relationship. This summary does not provide a definitive legal opinion for any factual situation. Before the firm can provide legal advice or opinion to any person or entity, the specific facts at issue must be reviewed by the firm. Before an attorney-client relationship is formed, the firm must have a signed engagement letter with a client setting forth the Firm’s scope and terms of representation. The information contained herein is based upon the law at the time of publication.

Notes

¹ Postmarks and Postal Possession, 90 Fed. Reg. 69,655 (Nov. 24, 2025). Available at https://public-inspection.federalregister.gov/2025-20740.pdf (last accessed January 16, 2026).

² First-year law students learn about the so-called Mailbox Rule as it applies generally. In federal tax law, it is contained in I.R.C. § 7502 and the regulations promulgated thereunder. States have their own versions, though many are not statutory and were established through case law. New York’s rule, which is described in Wester v. Casein Co., of Am., 206 N.Y. 506, 513 (N.Y. 1912) (“[W]hen one person by letter or telegram makes an offer to another and the other person accepts such offer, either by post or telegraph, the contract springs into existence at the time of such mailing or sending, because of implied authority in the carrier of the message to receive the reply”); see also Vassar v. Camp, 11 N.Y. 441 (1854).

³ Before 1954, tax documents were timely if physically delivered by the applicable deadline, but courts began to apply the common law mailbox rule to accommodate taxpayers who sent by mail and incurred delays without fault of their own. See Baldwin v. United States, 921 F.3d 836, 840 (9th Cir. 2019) (citing Arkansas Motor Coaches, Ltd. v. Commissioner of Internal Revenue, 198 F.2d 189, 191 (8th Cir. 1952)). The 9th Circuit in Baldwin explains that Congress addressed this issue with I.R.C. § 7502 and the IRS finalized Treas. Reg. § 301.7502-1 in 2011 which clarified that, “recourse to the common-law mailbox rule is no longer available.” This ruling, applied after the finalization of the Regulations, supersedes the 10th Circuit ruling in Sorrentino v. I.R.S., 383 F.3d 1187 (10th Cir. 2004), where a split court held that the common law mailbox rule is not necessarily void because of the § 7502 plain language. See also Philadelphia Marine Trade Ass'n-Int'l Longshoremen's Ass'n Pension Fund v. Comm'r, 523 F.3d 140 (3d Cir. 2008).

⁴ I.R.C. § 7502(a)(1). See, e.g., I.R.C. §§ 6511(a) (period to file claim for credit or refund of an overpayment) and 6072 (time for filing income tax returns).

⁵ See Treas. Reg. § 301.7502-1(c)(1)(iii)(A).

⁶ I.R.C. § 6651 provides a penalty for failure to file tax returns or pay a tax.

⁷ Treas. Reg. § 301.7502-1(c)(2).

⁸ Treas. Reg. § 301.7502-1(c)(1)(iii)(B).

⁹ See D.M.M. § 608.11.3.

¹⁰ Id.

¹¹ See D.M.M. § 608.11.4. USPS employees in the retail unit context automatically provide a local postmark.

¹² See D.M.M. § 608.11.3.