Mailing your tax return near the deadline comes with a risk that 'matters more now than ever'

If you're planning to mail in your 2025 tax returns this year, one detail may make the difference between filing on time and missing the deadline: a postmark.

While April 15 is when federal (and most state) taxes are due, the IRS considers any tax return postmarked on or before that date as being filed on time, even if it's not received by the agency until days later. A postmark shows the date your mail was processed and historically had been applied the same day you mailed an item.

However, due to ongoing operational changes at the U.S. Postal Service, the day you mail an item may not be when a postmark is applied. 

"The core issue is that taxpayers assume the day they drop a return in the mailbox is the day it gets postmarked," said Joshua Youngblood, founder of The Youngblood Group in Dallas and an IRS enrolled agent. "That has never been guaranteed, but it matters more now than ever."

As the Postal Service continues a multiyear overhaul of its operations to shore up its finances and modernize its infrastructure, the agency expects an increase in delays between when you mail something and when it receives a postmark, according to a published rule in the Federal Register that took effect Dec. 24.

Due to reduced pickups at many postal locations and increased travel times for mail to reach regional processing centers where postmarks are applied, "the postmark date does not inherently or necessarily align with the date on which the Postal Service first accepted possession of the mailpiece," the rule reads.

Although the Postal Service said in the notice that it is not modifying how mail is postmarked — that has always been done at its processing facilities — the agency added language to its Domestic Mail Manual to clarify the issue.

Part of the problem is that changes to transportation schedules and the consolidation of processing facilities mean many post offices that previously sent mail twice a day to a hub now do so only once in the morning, according to research from the Brookings Institution published in December. Additionally, about 26% of post offices are within 50 miles of their regional center, and another 26% are between 150 and 500 miles away, according to the research.

The upshot is that some mail generally doesn't begin moving through the system until at least the next day, in which case the postmark won't reflect the date you mailed the item. In some cases — i.e., ahead of weekends or holidays — it could take longer for it to be applied.

"To ensure that your tax return receives a postmark on the day you mail it, ask a retail associate at a post office retail counter to hand-cancel it for free," the Postal Service advises on its website.

Although households increasingly use digital options to file taxes, pay bills and handle other personal business, there are still people who use the Postal Service for time-sensitive mail, including tax returns.

So far in 2026, through March 27, the IRS had received 88.4 million tax returns. Of those, 1.6 million were not filed electronically. In 2025, of the 165.8 million tax returns received by the IRS, about 10.9 million were not e-filed, according to the agency.

For individual tax returns — i.e., your Form 1040 — the penalty for filing a late return is 5% of the tax due for each month or partial month the return is late, capping out at 25%. On top of that, the penalty for paying late is 0.5% of your unpaid balance per month, also capped at 25%. Interest is also charged on unpaid balances, accruing daily at the federal short-term rate plus 3%.

However, if you have filed and paid taxes owed on time over the previous three years, you can request that the penalties be waived, Youngblood said.

If you plan to mail your tax return, don't rely on metered postage or self-service kiosk labels, he said.

"Those show when the postage was printed, not when [the Postal Service] took possession," Youngblood said.

While it's free to ask a postal clerk to manually postmark your tax return, Youngblood said, you also can consider using certified mail, which costs $5.30.

"This gives you both proof of mailing and a reliable date stamp," he said. "It is the gold standard for anyone mailing something deadline-sensitive to the IRS."

Alternatively, a certificate of mailing, which you keep for your records, costs $2.40 and shows the date you mailed something. There also are private delivery services available that the IRS will accept correspondence from, Youngblood said.