Postmark delays can impact tax returns

• As of December 24, 2025, the date of the USPS postmark will likely be one or more days after the date the mail was collected by a letter carrier or dropped in a post box.
• Many federal, state, and local agencies use a postmark as the date of delivery or date of payment for tax returns, tax and fee payments, and ballots submitted by mail.
• Taxpayers and voters must take extra precautions to ensure their tax returns, payments, and ballots are postmarked by the applicable deadline.

The USPS adjusted its transportation operations effective December 24, 2025. Under the new Postmarks and Postal Possession rule, “The postmark date does not inherently or necessarily align with the date on which the Postal Service first accepted possession of the mailpiece.”
 

USPS postmarks are generally applied by machines at the originating processing facility, but mail often doesn’t arrive at an originating processing facility the same day it’s mailed. Because of that, explains the Postal Service, “the date on the postmarks applied at our 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.”
 

Taxpayers, take note: If you drop a tax return or payment in a mailbox or mail slot before the mail is picked up for the day, it could be postmarked on that date. More likely, it will be postmarked the next day or even later. Due to consolidation of local and regional processing facilities, your closest processing facility could be hundreds of miles from your local post office.

Many federal and state laws consider USPS postmarks as the date of delivery or payment for income taxes, property taxes, fees, fines, or other documents, including mail-in ballots.
 

Under federal law, for instance, if the USPS delivers tax payments, returns, or similar documents after the due date, “the date of the United States postmark … shall be deemed to be the date of delivery or the date of payment.” Thus, per the IRS, “Your return is considered filed on time if it is sent in an envelope that is properly addressed, has enough postage, is postmarked and deposited in the mail on or before the due date.”
 

The Washington State Department of Revenue points out how postmarks can work against state taxpayers: “If envelope is deposited in the mail by the due date but postmarked after the due date as a result of postal delay, then the return is delinquent and penalties are due,” unless certain circumstances are met. And New York has different due dates for different payment options; certified checks sent by mail must be postmarked one to four days earlier than other payment types.

Delaying application of a postmark could result in late tax returns and payments, which could lead to late fees, penalties, and interest charges for taxpayers. These can add up, increasing the overall cost of tax compliance for businesses (and increasing individual tax burdens for individuals).
 

Relying on postmarks as evidence for timely tax payment could be problematic even before the Postal Service adjusted its transportation practices: Postmark dates can be illegible, and envelopes can be lost or discarded. Nevertheless, taxpayers should try to ensure time-sensitive deliveries like tax payments and tax returns are postmarked by the due date.

How can taxpayers ensure tax returns are postmarked on time?

There are a few ways for taxpayers to make sure their tax returns are postmarked by the due date:

1. Mail tax payments and returns well in advance of the due date. (This is often easier said than done, especially for overworked tax teams or businesses operating on tight margins.)
2. Take your tax returns to a post office and request a manual (local) postmark at the retail counter. This service is provided free of charge.
3. Take your tax returns to the post office and purchase a Certificate of Mailing, which tax assessors may see as a good faith effort to mail your tax payment on time. Sending via Certified or Registered Mail, which are trackable and provide proof of receipt, offers additional protection. These options are not free.
4. Save yourself a trip to the post office and file and pay your taxes online. Noting the recent Postal Service changes, the Texas Comptroller is urging taxpayers to “utilize any automated report or payment system available, mail items early to ensure ample time for postal processing or have the mail clerk postmark your mail when you deliver it at the post office.”
    

If you need to use an overnight service, note that FedEx and UPS do not provide a valid U.S. postmark like USPS Priority Express. When overnighting a return, it’s best to ship at least two days before the deadline.

Bottom line for taxpayers

Tax returns and payments must be received by the due date, and most federal, state, and local laws treat the postmark as date of delivery or payment (i.e., official proof of timely filing). Tax administrators and assessors are unlikely to loosen requirements in response to the USPS policy change. 

“The attitude I’m seeing,” says Art Polk, Director of Property Tax Managed Services at Avalara, “is ‘don’t wait until the deadline,’ and ‘file or pay electronically on our website.’” Polk adds that local property tax returns stand to be impacted the most, as local jurisdictions have a lot of discretion when it comes to what is and isn’t late. 

Paying and filing taxes electronically sidesteps the postmark issue. However, some jurisdictions don’t accept online tax returns, especially for real and personal property taxes. “There are 20,000+ property tax assessors and collectors, many without online filing,” explains Polk. “Where online options exist, formats and requirements vary. In many cases, first-time filers cannot use e-filing without prior manual contact to establish accounts.”

In other words, mailing tax returns and payments is often the only option, and now more than ever, it’s a flawed one. Brian Smith, Senior Government Relations Director, suspects “delaying postmarks by one or more days will end up causing audit managers endless headaches.”

“The USPS postmark changes really underscore how risky it’s become to rely on mailing deadlines alone,” says Misti Tanzy, Senior Product Manager for Property Tax at Avalara. “Postmarks were already an imperfect safety net for taxpayers, and now they’re even less reliable. Mailing a return or payment on the due date no longer guarantees it will be treated as timely, which means taxpayers can do everything ‘right’ and still face penalties. This is especially challenging for property tax filings, where deadlines are strict, local rules vary widely, and electronic filing isn’t always available. When timing determines penalties, uncertainty is a problem.”

Solutions like Avalara Property Tax can help with compliance by speeding up calculation and return preparation, tracking tax bills, and enabling taxpayers to get filings and payments out the door earlier. Planning ahead, using documented proof of mailing, or filing electronically where possible are becoming essential ways to avoid postmark-related issues.