Roughly 19 million taxpayers asked the IRS for extra time to file their 2025 return this year, and that borrowed time runs out on October 15. For most of them the stakes are more than a scolding letter — a return that arrives more than 60 days after that date now triggers a minimum penalty of $525, regardless of how small the balance due actually is. The IRS built that floor specifically to stop taxpayers from treating a small tax bill as a reason to skip filing altogether.
Free File stays open, but only until the same deadline
In an August 26 reminder, the IRS urged extension filers to stop waiting and use IRS Free File, which remains available through October 15 for anyone with 2025 adjusted gross income of $89,000 or less. The program offers guided, no-cost preparation through IRS-vetted software partners, and taxpayers above that income threshold can still use Free File Fillable Forms if they are comfortable preparing their own return. Filing now rather than in the final days before the deadline gives a taxpayer time to catch an error, track down a missing document, or set up a payment arrangement before the window closes.
None of that changes what October 15 actually is under the tax code: the last day an extension is valid, not a second version of the April filing date with extra cushion. A return that isn’t filed by then is late, full stop, and the failure-to-file penalty clock starts running from that date.
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Two penalties that start on different dates
The IRS runs two separate penalty systems that people tend to conflate. The failure-to-file penalty punishes not submitting a return; the failure-to-pay penalty punishes not sending the money owed. An extension resets the clock on the first one but does nothing to the second — a taxpayer who filed for an extension in April to push their filing deadline to October 15 was still supposed to pay their estimated 2025 tax by the original spring due date. That is the detail buried in the IRS’s own line that an extension gives taxpayers more time to file but not more time to pay, language the agency repeats in nearly every extension-season release for a reason.
Both penalties can apply to the same taxpayer at once, and in months where they overlap, the IRS reduces the filing penalty by whatever the payment penalty already charged that month, so it works out to 4.5% failure-to-file plus 0.5% failure-to-pay rather than a full 5% stacked on top of another 0.5%. It is a small mercy, but it does not erase the incentive to file on time even without the money in hand.
How the 5 percent-a-month penalty climbs to its cap
The failure-to-file penalty is 5% of the unpaid tax for every month or partial month a return is late, capped at 25% of the unpaid balance. That means a taxpayer who owes $4,000 and files five months after October 15 could face the full 25% — $1,000 — on top of whatever they still owe the Treasury. The failure-to-pay penalty moves far more slowly, at 0.5% per month with the same 25% ceiling, which is exactly why the two get confused: they cap at the same percentage but accrue at ten times the speed of each other.
Why a flat $525 sits underneath the percentage
The percentage-based penalty has a floor for a reason: without one, a taxpayer who owes very little tax has almost no incentive to file at all. For any Form 1040 or Form 1120 due after December 31, 2025, which covers every 2025 return filed this extension season, a return filed more than 60 days late carries a minimum penalty of $525 or 100% of the underpayment, whichever is smaller. That figure climbs almost every year: it was $510 for returns due in 2025, $485 the year before that, and $450 the year before that, tracking inflation adjustments built into the penalty statute. A taxpayer who owes only $200 does not escape with a $10 percentage penalty; they owe the full $200, since 100% of the underpayment is less than $525 in that case.
Filing without paying still beats not filing at all
Because the two penalties accrue at such different speeds, the math almost always favors filing a return on October 15 even without full payment in hand. A taxpayer who files on time but cannot pay avoids the failure-to-file penalty entirely and faces only the slower 0.5%-per-month failure-to-pay charge, plus interest, until the balance is settled through a lump sum, an IRS Direct Pay transfer, or a payment plan. Skip the filing deadline entirely, and both the fast-accruing filing penalty and the $525 floor come into play on top of whatever is still owed. The IRS’s own guidance is blunt about the fix: apply for more time to file if genuinely needed, but treat October 15 as the real deadline it is, and pay as much as possible toward the balance regardless of whether the full amount is ready.
This article was produced with AI assistance and reviewed by a human editor. Figures are linked to their primary sources; where a claim could not be verified from the public record, we say so.
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