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What does an IRS penalty actually cost?
Most people assume an IRS penalty is catastrophic. Usually it's not. The underpayment rate is 8% annualized — cheaper than a credit card. The late filing penalty is a different story. See the real number for your situation.
2025 rates · Illustrative estimate · Not tax advice
What actually happens if you skip a payment:The IRS doesn't call. There's no audit flag. A small interest charge accrues on the shortfall and calculates automatically when you file in April — usually less than dinner for a typical missed quarter.
The amount you should have paid the IRS that quarter but didn't
The penalty runs until you pay the balance — usually through April 15
Your underpayment penalty
$30
8% annualized · 90 days · on $1,500
Less than a tank of gas.
8%
IRS rate
(annualized)
24%
Typical credit
card APR
The IRS is cheaper than a credit card. The penalty accrues at the federal short-term rate + 3%, prorated daily. It stops the moment you pay.
How to avoid it next time
Pay 100% of last year's tax bill in four equal quarterly installments — or 90% of this year's projected bill. Hit either safe harbor and the IRS cannot charge an underpayment penalty, even if you end up owing more in April.
First-time penalty abatement:If this is your first offense and you've filed on time in prior years, the IRS will often waive the penalty entirely. Worth asking before you pay.
Estimates only. Underpayment rate is 8% (federal short-term rate + 3%) as of 2025 Q1, adjusted quarterly by the IRS. Late filing and payment penalties per IRC §6651. When both filing and payment penalties apply in the same month, the late filing penalty is reduced by the payment penalty amount — the combined rate is 5%/month, not 5.5%. Minimum late filing penalty of $510 applies when a return is more than 60 days late. Not tax advice — consult a CPA for your specific situation.
Also read
I Missed a Quarterly Tax Payment — What Actually Happens?
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Read Tax planningHow to Pay Quarterly Taxes as a Small Business Owner
What estimated taxes are, when they're due, and how to avoid surprise bills by saving the right amount throughout the year.
Read Tax planningYear-Round Tax Calendar
Every quarterly estimate deadline, filing deadline, and planning milestone for self-employed business owners — in one place.
ReadWork with Matt
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Tax services provided through Matt Reese, CPA. This page is educational and does not constitute tax or investment advice.