Convert $75,000 to a Roth in February and Pay the Tax With the Return 14 Months Later, and the IRS Charges Interest for Every Month in Between, About $1,100. Send One Quarterly Payment in April Instead and the Charge Is $0
A February Roth conversion quietly starts a clock most people never see, and by the time they file their return over a year later, the IRS has already calculated what they owe for being late on a tax bill they…
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Let’s assume you are doing a Roth conversion to move money from a traditional IRA to a Roth IRA, which means the converted dollars count as ordinary income for that year. IRS guidance says those amounts are “normally included in income on your return for the year that you converted them”. Many converters miss the timing problem. For example, if you convert $75,000 in February 2026 and file that year’s return in April 2027, the IRS treats the time in between as an underpayment of estimated tax.
Depending on the bracket, the charge runs from about $770 to roughly $1,100. One estimated payment sent by April 15, 2026 brings it to zero.
How a February Conversion Turns Into Four Deadlines
The tax code expects you to pay income tax as you earn it. It sets 4 required installments each year, due April 15, June 15, September 15, and January 15 of the following year. Each installment is 25% of the required annual payment. IRS Publication 17 warns that converters “may have to increase your withholding or make estimated tax payments”.
Each missed piece is charged separately, from its due date until it is paid or until the 15th day of the 4th month following the close of the taxable year. For a 2026 conversion, that means April 15, 2027. The April piece therefore remains unpaid for a full year, while the January piece is only a few months late.
Running the Numbers on a $75,000 Conversion
By law, the penalty rate equals the Federal short-term rate plus 3 percentage points. The Fed’s target range tops out at 4% as of October 20, 2026, so a working estimate is about 7%. The IRS resets the rate each quarter. The charge is simple interest because the daily compounding rule doesn’t apply to estimated-tax penalties.
In the 22% bracket, the conversion adds $16,500 in tax, or $4,125 per quarter.
The April piece costs about $289 over its full year of delay, and the January piece costs about $71. Here is the total penalty by bracket, using IRS bracket rates:
- 22% bracket: $16,500 of conversion tax, penalty of about $768
- 24% bracket: $18,000 of conversion tax, penalty of about $838
- 32% bracket: $24,000 of conversion tax, penalty of about $1,117
The $1,100 figure applies to households whose conversion is taxed at 32%. For single filers in 2025, that rate started at $197,301 of taxable income.
A middle-income converter in the 22% bracket pays closer to $770. In both cases, the charge buys nothing, since the Roth balance is the same whether you take the tax hit in April 2026 or a year later. (The bigger question, whether to convert at all, usually turns on which bracket you expect in retirement, something we walked through in a free guide to the low-tax window before RMDs begin.)
Why One April Payment Wipes Out the Charge
Estimated payments are applied in the order in which such installments are required to be paid. A single $16,500 payment by April 15 covers the first installment, and the extra carries forward to cover June, September, and January. Pay every installment on time, so no underpayment period ever begins.
Paying early does have a cost: the cash leaves the account a year sooner and stops earning interest. With a 10-year Treasury yield of 5.15%, that lost interest is real money. Some converters would rather keep earning on the cash and accept the penalty. Most never make that choice on purpose. They simply don’t see the clock started in April.
Who Owes Nothing Even Without an April Payment
Many converters are protected by the safe harbor. The required annual payment is the lesser of 90% of the current year’s tax shown on the return or 100% of the prior year’s tax. That second figure rises to 110% when prior-year AGI exceeded $150,000.
If paycheck withholding already matches last year’s total tax, the conversion tax can wait for the return with no penalty. The good news is that no penalty applies either when the balance due is less than $1,000.
Withholding gets favorable treatment because, unless the taxpayer chooses otherwise, an equal part of such amount shall be deemed paid on each due date, so extra withholding in November counts as if it had been spread across all four quarters. Advisors are also openly asking when a conversion is worth the squeeze at all. A surprise penalty only worsens the math.
Steps That Keep the Penalty at Zero
- Check last year’s total tax before converting. If current withholding already covers 100% of that figure (110% for higher earners), the conversion tax can wait until the return.
- If withholding falls short, send the conversion tax with the April 15 estimated payment for the conversion year. Paying in full on the first deadline covers all four installments.
- If April has already passed, raise W-4 withholding for the rest of the year. Because withholding is treated as paid evenly, it can still retroactively cover the earlier quarters.
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David Beren has been a Flywheel Publishing contributor since 2022. Writing for 24/7 Wall St. since 2023, David loves to write about topics of all shapes and sizes. As a technology expert, David focuses heavily on consumer electronics brands, automobiles, and general technology. He has previously written for LifeWire, formerly About.com. As a part-time freelance writer, David’s “day job” has been working on and leading social media for multiple Fortune 100 brands. David loves the flexibility of this field and its ability to reach customers exactly where they like to spend their time. Additionally, David previously published his own blog, TmoNews.com, which reached 3 million readers in its first year. In addition to freelance and social media work, David loves to spend time with his family and children and relive the glory days of video game consoles by playing any retro game console he can get his hands on.
