One common approach to paying Roth conversion tax with IRA withholding is to elect federal (and state) tax to be withheld directly from an IRA distribution. Because withholding is treated as paid evenly across the whole year, a single December election can cure an underpayment penalty that skipped quarterly estimates would otherwise leave in place.
Tax withheld from an IRA is deemed paid evenly across all four quarters, unlike an estimated payment, which is credited only on the day you send it. So a lump-sum year-end withholding can retroactively erase an underpayment penalty on a late Roth conversion. The catch: withheld dollars leave the IRA, shrink the Roth, and, if you are under 59½, can trigger a 10% early-distribution penalty.
The withholding “trick,” in one sentence
The idea sometimes called the withholding “trick” is simple: instead of scrambling to fix skipped quarterly estimates, you have your custodian withhold federal tax from an IRA distribution late in the year, and the tax code treats that withholding as if it had been paid steadily since January. That timing quirk is what can neutralize an underpayment penalty on a Roth conversion.
The rule that makes it work: withholding is treated as paid evenly all year
Under IRC 6654(g)(1), amounts withheld from wages, pensions, or IRA distributions are treated as paid in equal parts on each estimated-tax due date, regardless of when the withholding actually happened. A lump-sum withholding on December 31 is therefore treated as though one quarter of it was paid back on the first estimated deadline in April, another quarter in June, another in September, and the last in January. That “paid evenly” fiction is the entire mechanism.
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Estimated payments get credited the day you pay them; withholding does not
An estimated tax payment is credited only as of the date you send it. If you make one big estimated payment in December, the earlier quarters still show a shortfall, and the penalty for those quarters stands. Withholding behaves differently, and that difference is the edge. For readers weighing whether to convert at all, our overview of the Roth conversion strategy and the companion piece on how much to convert cover the upstream decision.
How “paid evenly throughout the year” actually saves you
The federal underpayment penalty is really interest, charged quarter by quarter on the amount you fell short. Estimated payments only stop the meter from the date they land. Withholding, because it is spread back across every quarter, can plug the gap in Q1, Q2, and Q3 at the same time, even if the dollars did not exist until the final weeks of the year.
Worked example: converted in Q4, skipped the earlier estimates
Illustrative example, hypothetical figures only. Suppose you convert $100,000 in December and elect $22,000 of federal withholding on that distribution. Under the paid-evenly rule, the IRS treats $5,500 as remitted on each of the four estimated-tax dates (April 15, June 15, September 15, and the following January 15). If you paid nothing earlier in the year, that retroactive spread can erase the shortfall for the earlier quarters rather than leaving three quarters of penalty on the books.
The safe-harbor targets your withholding must hit
Withholding only helps if it carries you to a safe harbor. Most taxpayers avoid the penalty by hitting the smaller of two targets. The 110% figure applies once prior-year adjusted gross income crosses $150,000 (or $75,000 if married filing separately).
| Safe harbor | What you must pay in (via withholding plus estimates) |
|---|---|
| Current-year test | At least 90% of this year’s total tax |
| Prior-year test (AGI $150,000 or less) | At least 100% of last year’s total tax |
| Prior-year test (AGI over $150,000) | At least 110% of last year’s total tax |
The prior-year test is often the friendlier one, because a big conversion inflates current-year tax and makes 90% a moving target. If your withholding reaches 100% or 110% of last year’s tax, the extra conversion income generally will not create a penalty even before you file.
Step by step: paying the conversion tax straight out of the IRA
Paying the tax from inside the IRA is a matter of the withholding election on the distribution paperwork. The mechanics are straightforward, but three details decide how much actually reaches the Roth and whether a second tax bill is waiting: the election percentage, the gross-versus-net question, and state tax.
Electing 0% to 100% withholding on the conversion distribution
On an IRA distribution you can generally elect any federal withholding rate from 0% to 100%. If you say nothing, the custodian’s default is 10%. For a conversion where the goal is to hit a safe harbor, many investors set the election deliberately rather than accept the default, since 10% rarely matches a conversion-year tax rate.
Convert-gross versus convert-net: withheld dollars are a distribution, not a conversion
This is the trade-off at the heart of the strategy. Any dollars withheld for tax do not land in the Roth: they are a taxable distribution sent to the IRS. Convert $100,000 with $22,000 withheld and only $78,000 reaches the Roth, yet you are taxed on the full $100,000. To move the entire $100,000 into the Roth, you would need to cover the tax from outside cash. The Roth conversion break-even math shifts noticeably depending on which path you choose.
State withholding is a separate election
Federal withholding from an IRA does not satisfy a state tax obligation. If you live in a state with income tax, you generally need a separate state withholding election on the distribution or a state estimated payment. Some custodians apply a state default and some do not, so the state box is worth checking rather than assuming.
The under-59½ landmine, and the 60-day fix that saves the play
For younger converters the withholding route carries a hidden cost. Dollars withheld for tax are not converted, so the IRS sees them as an early distribution. That is a major reason the withholding approach is generally suited to those already past 59½, and why under-59½ readers usually pay the tax from outside cash instead.
Withheld dollars equal an early distribution: the 10% penalty risk
If you are under 59½, the withheld amount (not the converted amount) is treated as an early distribution. That means ordinary income tax plus a 10% early-distribution penalty on those withheld dollars. In the example above, the 10% would apply to the $22,000 that went to the IRS, adding roughly $2,200 on top, which quietly undoes much of the convenience.
The 60-day workaround: replace the withheld amount from taxable savings
There is a repair. Within 60 days you can deposit an amount equal to the withheld dollars into the Roth from outside savings, completing the conversion and removing the early-distribution character of those dollars. Two constraints matter: the deposit must happen inside the 60-day window, and a Roth conversion is not itself subject to the once-per-12-months IRA rollover limit, but the replacement deposit should still be coded as a conversion contribution, so confirm the coding with the custodian. Early retirees running a Roth conversion ladder should weigh this carefully before relying on withholding.
When to skip withholding and use estimates plus Form 2210 instead
The withholding route is not the default answer for everyone. If you are comfortably past 59½ and want to keep every dollar compounding tax-free inside the Roth, paying the tax from a taxable account and handling the timing through estimated payments is a common alternative. Two tools make that path work cleanly.
Paying tax from a taxable account can preserve tax-free growth
Every dollar used to pay tax from inside the IRA is a dollar that stops growing tax-free. Illustrative example: $22,000 left inside a Roth and compounding at 7% for 20 years would grow to roughly $85,000. Paying that same tax from a taxable account keeps the full conversion working inside the Roth. One approach is to make a single Q4 estimated payment by January 15 to cover a late conversion.
Annualizing income on Form 2210 Schedule AI
If the conversion income truly landed in the fourth quarter, Form 2210 Schedule AI (the annualized income installment method) lets you show the IRS that the income arrived late in the year rather than evenly. That can reduce or remove the penalty for the earlier quarters, because the default assumption of even quarterly income is what created the shortfall in the first place. The method requires documenting income and deductions period by period, which is more paperwork than a withholding election but avoids pulling money out of the IRA.
Two paths compared
The choice usually comes down to age and where the tax dollars sit. Households already past 59½ who missed estimates often lean toward withholding, while those focused on preserving tax-free growth tend to pay from a taxable account and manage the timing with estimated payments. The table below summarizes the trade-offs, and the December 31 conversion deadline applies to both.
| Factor | Pay tax via IRA withholding | Pay tax from taxable account plus estimates |
|---|---|---|
| Penalty timing | Deemed paid evenly all year; can cure skipped quarters | Credited when paid; may need Form 2210 Schedule AI to annualize |
| Amount reaching the Roth | Reduced by the withheld dollars | Full conversion reaches the Roth |
| Under-59½ impact | Withheld dollars can trigger the 10% penalty unless replaced within 60 days | No early-distribution issue on the tax dollars |
| Typical audience | Often those 59½ or older who missed estimates | Often those preserving more tax-free growth |
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Frequently asked questions
What is the IRS underpayment penalty rate right now?
For the third quarter of 2026 (July 1 through September 30), the individual underpayment rate is 7%, calculated as the 4% federal short-term rate plus 3 percentage points under IRC 6621. The interest compounds daily, and the IRS resets the rate every quarter, so it can move up or down from one three-month period to the next.
How much can the penalty actually cost in dollars?
Illustrative example: a $20,000 shortfall carried for roughly a year at the current 7% rate, compounded daily, runs to about $1,400. Because the charge is really interest that accrues quarter by quarter, curing the shortfall earlier (or spreading withholding back across the year) reduces the number. Actual amounts depend on the size and duration of each quarter’s shortfall.
Do the safe-harbor thresholds change if my AGI is higher?
Yes. You generally avoid the penalty by paying in the smaller of 90% of this year’s tax or 100% of last year’s tax. Once prior-year adjusted gross income exceeds $150,000, the prior-year target rises to 110%. For married filing separately, that higher threshold starts at $75,000 of AGI. A large conversion often makes the prior-year test the easier one to reach.
If I convert $100,000 and withhold $22,000, how much lands in the Roth?
Illustrative figures: $78,000 lands in the Roth, because the $22,000 withheld for federal tax is a distribution sent to the IRS, not a conversion. You are still taxed on the full $100,000. Under the paid-evenly rule, that $22,000 is treated as $5,500 remitted on each of the four estimated dates: April 15, June 15, September 15, and the following January 15.
Does a December withholding erase the penalty for Q1 through Q3?
Often, yes. Because withholding is deemed paid evenly across all four quarters, a large December withholding is treated as if part of it was paid on each earlier deadline. If the retroactively spread amount lifts you to a safe harbor, it can cure the earlier-quarter shortfall rather than leaving three quarters of penalty in place. The result depends on hitting a safe-harbor target.
What is the default IRA withholding percentage?
If you make no election on an IRA distribution, the custodian’s federal default is 10%. You can generally elect any rate from 0% to 100% instead. For a conversion, 10% rarely matches the conversion-year tax rate, so many investors set the percentage deliberately to reach a safe harbor rather than accepting the default.
I am under 59½: what does the withheld amount cost me?
The withheld dollars (not the converted dollars) are treated as an early distribution: ordinary income tax plus a 10% early-distribution penalty on that amount. On $22,000 withheld, the 10% adds roughly $2,200. This is why paying the tax from outside cash is often the more sensible route for those under 59½, unless they use the 60-day replacement fix.
How does the 60-day rollover fix work?
Within 60 days you can deposit an amount equal to the withheld dollars into the Roth from taxable savings, completing the conversion and removing the early-distribution treatment on those dollars. The timing is strict: the deposit must land inside the 60-day window. A Roth conversion is not subject to the once-per-12-months IRA rollover limit, but the replacement should be coded as a conversion contribution, so confirm the coding with your custodian.
Does IRA federal withholding also cover my state tax?
No. Federal withholding from an IRA does not satisfy a state income tax obligation. In a state with income tax you generally need a separate state withholding election on the distribution or a state estimated payment. Custodian handling varies, so it is worth confirming the state box rather than assuming a default was applied.
What are the estimated-tax due dates for a late conversion?
The four federal estimated-tax dates are April 15, June 15, September 15, and January 15 of the following year. January 15 is the last date to make a Q4 estimated payment covering a conversion done late in the year. Note that RMDs must be taken before converting in an RMD year; see the 2026 RMD rules for that sequencing.
