You filed the extension in April. October 15 is almost here. You’ve already counted on a penalty for paying your estimates late, and you figure filing late made it worse.
It probably didn’t. Depending on what you paid last year, you may owe less than you think, or nothing at all.
The underpayment penalty on Form 2210 doesn’t care when you file. It cares about what you paid, and when you paid it, while 2025 was still going on. Tax compliance is not a once-a-year event. The IRS scores your payments quarter by quarter. It checks them against your return when the return finally shows up, and then it mails you a bill based on what it sees. If you know how that scoring works, you can still claim protection the IRS won’t hand you on its own. Not sure which side of the line you landed on? Steve Perry, EA can check your 2025 payments against the safe harbor tests before you file. That way the penalty line on your return is a number you chose, not one the IRS chose for you. Call 678-717-9818, email steve@bookstaxesatl.com, or connect on LinkedIn at www.linkedin.com/in/steveperrybtm.
The Clock Stopped in April
Your 2025 estimated tax was due in four pieces: April 15, June 16, and September 15, 2025, and January 15, 2026. The IRS Instructions for Form 2210 say the penalty is figured separately for each one. Pay too little in April and too much in December, and April still gets penalized, even if the year evens out.[irs]
But the meter doesn’t run forever. For each payment, the penalty stops on the date you paid or on April 15, 2026, whichever came first. After that, the Form 2210 penalty is frozen. Filing in October doesn’t add a single dollar to it. Any balance you still owe moves into a different bucket: the failure to pay penalty and interest. That bucket is a separate conversation.
Your Safety Nets Survived the Extension
If your 2025 payments cleared any one of these bars, the penalty may go away completely:
- You owe less than $1,000 after withholding.
- You paid at least 90% of your 2025 tax on time.
- You paid at least 100% of your 2024 tax on time, or 110% if your 2024 AGI was over $150,000 ($75,000 married filing separately).
- You had zero tax liability for 2024, for a full 12 month year, as a U.S. citizen or resident.
- You are a farmer or fisher who meets the income test, so the 90% drops to 66 2/3%.
Other exceptions may apply depending on the facts and circumstances. An extension didn’t cancel any of them.
The Trap Hiding in Last Year
The prior year test is the favorite safe harbor for a reason. You know the target in January, so you can hit it on purpose. But there’s a catch. The Form 2210 instructions say you can’t use it if you never filed a 2024 return. No 2024 return, no prior year protection. That leaves you with the 90% test. If your income jumped, 90% of a bigger number is a much harder target.
Now look ahead. The 2025 return you’re about to file becomes your prior year number for 2026. Skip it or let it slide, and you lose next year’s easiest safe harbor too. One missed filing quietly weakens two years. If 2024 or 2025 is still unfiled, that’s the first thing to fix. Filing them in the right order is exactly where Steve Perry, EA can help. Before that gap costs you another year of protection, call 678-717-9818, email steve@bookstaxesatl.com, or connect on LinkedIn at www.linkedin.com/in/steveperrybtm.
What Filing Late Does Cost You
Two things. The first is interest on the penalty itself. File by April 15 and pay the bill on time, and the IRS charges no interest on the penalty. Extended filers lose that break. The IRS underpayment rate for the fourth quarter of 2026 is 7% a year, compounded daily.[irs]
The second, and bigger, cost is losing control of the math. Leave Form 2210 off the return, and the IRS figures the penalty for you and then sends a CP30 notice. Its calculation assumes your income and your withholding came in evenly all year. It has no idea you landed a big contract in November or sold property in December.[irs]
Money Left on the Table
These reductions exist, but only if you file Form 2210 and check the right box:
- The annualized income method on Schedule AI, made for people whose income showed up late in the year.
- Counting withholding on the actual dates it came out, when that helps.
- A waiver for a casualty, disaster, or other unusual circumstance.
- A waiver if you retired after age 62 or became disabled in 2024 or 2025 and had reasonable cause.
There may be others depending on the facts and circumstances. Every one of them depends on records: when income came in, payment confirmations, pay stubs, and proof of the event behind a waiver. No paperwork, no reduction. The IRS number stands.
The 2026 Move You Still Have Time to Make
Now look at this year. Your last 2026 estimate is due January 15, 2027. Withholding has a big advantage over estimated payments. The IRS treats it as if it came in evenly all year, even if you withheld it all in December. Raise the withholding on your paycheck or certain retirement distributions this fall, and you can cover earlier quarters that a late estimate can’t reach. That window closes with your last paycheck of the year.
The Real Risk Is What Happens Next
Tax planning and IRS risk management don’t stop when you hit submit. Most IRS headaches don’t start with a filing mistake. They start with what people don’t do after the return is filed, after the notice shows up, or after they spot an opportunity and let it pass. The safe harbors reward people who paid on time, kept their records, and claimed what they were owed.
You’re about to file. That makes right now the cheapest moment to get the penalty right and set up 2026 so this doesn’t happen again. Bring your 2025 payment history to Steve Perry, EA, and leave with a clear answer on the penalty and a plan for the fourth quarter. Call 678-717-9818, email steve@bookstaxesatl.com, or connect on LinkedIn at www.linkedin.com/in/steveperrybtm.
Frequently Asked Questions
Does filing on extension make my Form 2210 penalty bigger?
No. The penalty stopped growing on the date you paid or on April 15, 2026, whichever came first. Filing late can add interest on the penalty, plus charges on any unpaid balance.
Do I have to file Form 2210?
Usually not. The IRS will figure the penalty and bill you. But you need the form to claim a waiver, use the annualized method, or count withholding on its actual dates, among other situations.
Can I use the prior year safe harbor if I never filed for 2024?
No. Without a 2024 return, you’re measured against 90% of your 2025 tax.
What if I lived in a federally declared disaster area?
The IRS usually identifies covered taxpayers and applies relief on its own. You usually don’t file Form 2210 for that reason alone unless you’re using the annualized method.
I already got a CP30. Is it too late?
Not necessarily. If the IRS missed a waiver, or the annualized method would lower the bill, you may be able to respond. Send the notice to Steve Perry, EA and find out whether that number should stand before you accept it as final. Call 678-717-9818, email steve@bookstaxesatl.com, or connect on LinkedIn at www.linkedin.com/in/steveperrybtm.
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