USPS postmarks can lag mailing dates. What taxpayers and voters should know

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U.S. Postal Service postmark practices that were formalized in a December 2025 rule could mean a longer delay between when something is mailed and when it's postmarked — a distinction that matters for tax returns, mail-in ballots and other time-sensitive documents.

The issue may crop up as two deadlines approach: Oct. 15 for taxpayers who received a six-month extension to file their federal income tax returns, and Nov. 3 for voters casting ballots in the midterm elections.

Taxpayers who mail their return can meet Thursday's deadline by taking it to the post office for a manual postmark. But voters casting ballots by mail for the midterms can't necessarily count on the same rule.

That's because while the IRS generally considers a return filed on the day it is postmarked, most states require mail-in ballots to arrive by Election Day, regardless of when they were mailed or postmarked. A postmark shows the date your mail was processed, which may not be the day you mailed the ballot. 

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Thirty-five states require mailed absentee ballots to be received by election officials on or before Election Day, according to the National Conference of State Legislatures, a bipartisan organization that tracks state laws and policies. The other 15 states — along with Washington, D.C., Guam, Puerto Rico and the Virgin Islands — generally allow ballots postmarked by Election Day to arrive afterward, usually within a specified number of days.

"State laws govern elections for the most part, and every state has chosen a little bit different way of doing things," said Katy Owens Hubler, director of elections and redistricting for the NCSL.

Nearly 48 million voters cast absentee ballots in the 2024 presidential election, representing roughly 30% of the total 158.2 million ballots cast, according to the U.S. Election Assistance Commission. The absentee figure includes mail-in ballots as well as those returned through drop boxes or in person.

About 1.2% of the mail-in ballots cast in 2024 were rejected, according to the commission. Of them, 40.7% were rejected because the signature on the return envelope didn't match the one on file or was incomplete, and 10% were rejected because they lacked any signature. Another 17.8% were rejected because they were not received by the state's deadline.

Those deadlines vary from state to state. In California, for instance, mail-in ballots postmarked by Election Day can arrive as many as seven days afterward and still be counted, according to NCSL. Colorado, by contrast, requires mail-in ballots to be received by 7 p.m. on Election Day. Some states give military and overseas voters additional time for ballots to arrive after Election Day.

In a June ruling, the Supreme Court upheld states' authority to count mail-in ballots received after Election Day, provided they were cast on time and meet state deadlines.

Voters should be aware that, generally, it may take longer than they expect for ballots to reach election offices, and that postmarks may not be applied the day they mail their ballot.

This is because the U.S. Postal Service has been overhauling its operations, which over time has included reduced pickups at many postal locations and increased travel times for mail to reach regional processing centers where postmarks are applied. The upshot is that the agency expects longer delays between when mail is sent and when it is postmarked, according to a Postal Service rule that took effect in December 2025.

In practice, this means some mail doesn't begin moving through the system until at least the day after you mail it, so the postmark isn't applied the day you mailed it. In some cases — i.e., ahead of weekends or holidays — it could take longer for a postmark to be applied, according to the Brookings Institution, a think tank.

However, beginning on Oct. 24, the Postal Service said it plans to use "extraordinary measures" to speed up delivery of mail-in ballots ahead of the Nov. 3 election — such as making additional deliveries to election offices. Starting on Oct. 26, postal workers are also supposed to hand-postmark ballots being delivered directly to local election offices or routed through postal hubs to other election offices, according to a USPS memorandum.

"These things are going above and beyond what the Postal Service does for other pieces of mail," said Tammy Patrick, chief programs officer at the National Association of Election Officials, a nonprofit organization for election administrators.

Nevertheless, those actions don't guarantee your ballot will arrive by your state's deadline.

For voters who will mail in their ballot, "try to get it in the mail a week before it's due," Patrick said. "If it's closer to Election Day and they live in a state that allows for a postmark [to establish a deadline is met], they can go into any post office and go up to the counter and ask to have it be hand-postmarked."

Meanwhile, taxpayers who file their return online can avoid the postmark issue altogether. Those who need to mail their return should ask a postal worker for a manual postmark, or send it via certified mail.