Do You Owe Estimated Taxes After a Roth Conversion? (w/Examples) + FAQs

This article reflects federal IRS rules and general state rules as of June 2026 and covers tax years 2025 and 2026. Tax law changes — confirm current figures before you file.

Quick Answer: Maybe. A Roth conversion adds taxable income, so you may owe estimated taxes for tax year 2026 — but only if your total withholding and payments fall short of a “safe harbor.” Pay 90% of this year’s tax, 100% of last year’s (110% if 2025 AGI topped $150,000), or owe under $1,000, and you skip the penalty.

A Roth conversion moves money from a pre-tax retirement account into a Roth account, and the converted amount counts as ordinary income in the year you convert. That extra income can push your total tax bill far past what your paycheck or pension withholds, and the IRS expects tax paid as income is earned — not all at once next April. Miss that timing, and you face an underpayment penalty calculated at the federal short-term rate plus 3%, which sat at 8% for much of 2024–2025.

The stakes are real and the clock is ticking. The IRS reports it assessed penalties on roughly 14 million taxpayers for underpaying estimated tax in recent years, and a single large conversion can drop you into that group overnight. Here is what you will learn:

💡 How the safe-harbor rules decide whether you owe anything at all.
🧮 Worked dollar examples showing exactly how much to pay and when.
🗓️ The four 2026 estimated-tax deadlines and what happens if you blow one.
🔁 The withholding “trick” that erases penalties even for a December conversion.
⚠️ The seven most common mistakes that trigger surprise IRS penalties.

What a Roth Conversion Does to Your Taxes

A Roth conversion is when you move money from a traditional IRA, 401(k), or other pre-tax account into a Roth IRA. You paid no tax on that money going in, so the IRS taxes it on the way over. The entire converted amount (minus any after-tax basis) gets added to your ordinary income for the year, taxed at your regular rates — not the lower long-term capital gains rates.

That single change ripples through your whole return. A $100,000 conversion does not just create tax on $100,000. It can push you into a higher bracket, raise the tax on your other income, trigger higher Medicare IRMAA premiums two years later, make more of your Social Security taxable, and phase out credits and deductions. The consequence of ignoring this is a tax bill that arrives with no money withheld to cover it.

Here is the core problem the IRS cares about: the United States runs a pay-as-you-go tax system. You are expected to pay tax as you receive income, through paycheck withholding or quarterly estimated payments. A conversion is income with zero withholding by default, so unless you act, you fall behind. The penalty for falling behind is not a flat fine — it is interest charged on the shortfall for each day it stays unpaid.

What you should do: before you convert, estimate the added tax (your marginal rate times the conversion amount is a fast starting point), then decide how you will cover it — withholding, an estimated payment, or a safe-harbor strategy explained below.

The Safe-Harbor Rules That Decide If You Owe

You do not owe an estimated-tax penalty — even with a big conversion — if you meet any one of the IRS safe-harbor tests for Form 2210. Meeting just one is enough. This is the single most important concept in the entire topic, so read it twice.

The $1,000 Floor

If your total tax owed after subtracting withholding and credits is less than $1,000 for the year, you owe no penalty. This is the simplest escape hatch. If your withholding already nearly covers your conversion, a small shortfall under $1,000 costs you nothing in penalty. The consequence of forgetting this rule is overpaying out of fear when you did not need to. Check this floor first before sending any extra payment.

The 90%-of-Current-Year Test

You are safe if your payments cover at least 90% of the tax you actually owe this year. For a 2026 conversion, that means paying in 90% of your final 2026 tax through withholding plus timely estimates. The catch: you must estimate your full-year tax accurately, which is hard mid-year. Miss the estimate low and you fall short. Use this test when your income is predictable or the conversion is your only surprise.

The 100%/110%-of-Prior-Year Test (the Safe One)

This is the test most converters should aim for because it uses a known number — last year’s tax. You are protected if you pay 100% of your prior-year total tax. But if your prior-year AGI was over $150,000 ($75,000 if married filing separately), the bar rises to 110% of prior-year tax. The beauty here: you can convert $1 million and still owe zero penalty, as long as you paid in 110% of last year’s tax on time. You settle the rest of the bill by April 15 without penalty.

How Withholding Beats Estimated Payments (the Key Trick)

The most powerful tool for a conversion is withholding, and most people miss why. The IRS treats withholding as paid evenly throughout the year, no matter when it was actually withheld. Estimated payments, by contrast, are credited only when you actually pay them.

That timing difference is everything. If you do a conversion in December and withhold the tax directly from the distribution or from a year-end IRA withdrawal, the IRS acts as if you paid it in equal amounts since January. A December estimated payment, on the other hand, is treated as late for the first three quarters — and the penalty clock runs on those quarters.

The consequence of using the wrong tool: a converter who sends a $24,000 estimated payment in January pays a penalty for Q1 through Q3, while a converter who withheld the same $24,000 in December owes nothing. Same dollars, very different outcome.

What you should do: when converting late in the year, ask your IRA custodian to withhold federal tax from the distribution, or take a separate IRA distribution near year-end with heavy withholding to true up. Note that withholding from the conversion itself reduces how much lands in the Roth, so many people withhold from other funds instead.

Which Situation Applies to You?

The answer changes based on when you convert and what your numbers look like. Find your row.

You already pay quarterly estimates and convert in Q1 or Q2: add the conversion tax to the matching quarter’s payment, or lean on the prior-year safe harbor.
You convert late (Q3 or Q4): use the withholding trick or file Form 2210 Schedule AI to annualize.
Your 2025 AGI was over $150,000: you must hit the 110% prior-year bar, not 100%.
Your withholding already exceeds 110% of last year’s tax: you owe no estimated payments at all, regardless of the conversion size.
You expect to owe under $1,000 after withholding: you are done — no estimates needed.

Worked Example: A Q1 Conversion

Meet Linda, age 64, married filing jointly. Her 2025 total federal tax was $18,000, and her 2025 AGI was $140,000 (under the $150,000 line, so her bar is 100%). In March 2026 she converts $100,000 from her traditional IRA. Her marginal rate is 22%, so the conversion adds roughly $22,000 in tax.

Her safe-harbor target is 100% of 2025 tax = $18,000. Her pension withholds $12,000 across 2026. She needs $6,000 more in timely payments to reach $18,000. Because she converted in Q1, she pays $1,500 per quarter ($6,000 ÷ 4) on April 15, June 15, September 15, 2026, and January 15, 2027.

By doing this, Linda meets the prior-year safe harbor and owes zero penalty, even though her actual 2026 tax (with the conversion) will be near $40,000. She simply pays the remaining balance by April 15, 2027. The math:

What Linda Does	What It Produces
Pension withholding of $12,000	Covers most of her base tax
Four estimates of $1,500 each	Brings total paid-in to $18,000
Reaches 100% of 2025 tax on time	Penalty = $0, balance due in April 2027

Worked Example: A High-Income Converter

Meet Marcus, age 58, single. His 2025 AGI was $200,000 — over the $150,000 threshold — so his bar is 110% of prior-year tax. His 2025 total tax was $40,000, making his safe-harbor target $44,000 ($40,000 × 110%). In July 2026 he converts $300,000.

Marcus’s salary withholds $36,000 for 2026. To hit safe harbor he needs $8,000 more in timely estimates. He splits it across the remaining 2026 deadlines. He ignores the giant actual tax on the $300,000 conversion until filing, because the 110% rule shields him from penalty.

Marcus’s Move	The Result
Salary withholding of $36,000	Base coverage toward the $44,000 target
$8,000 in timely estimates	Reaches 110% of 2025 tax
Hits $44,000 safe harbor	No penalty despite a $300,000 conversion

Worked Example: The December Conversion Rescue

Meet Priya, age 67, married filing jointly. She forgot about estimates and converts $80,000 on December 20, 2026. She made no estimated payments all year and her withholding falls short of every safe harbor. A normal estimated payment now would trigger penalties for Q1–Q3.

Instead, Priya converts and instructs her custodian to withhold $20,000 in federal tax from a companion year-end IRA distribution. Because withholding counts as paid evenly all year, the IRS treats that $20,000 as if paid in four equal pieces since January. Her shortfall vanishes and her penalty drops to $0. This is the rescue move for procrastinators.

Form 2210 and Schedule AI: A Walkthrough

Form 2210, “Underpayment of Estimated Tax by Individuals, Estates, and Trusts,” is where the penalty gets calculated. You file it with your Form 1040 by the April deadline. Often the IRS computes the penalty for you, but you file 2210 when you want to reduce it.

When You Must (or Want to) File It

You generally do not need to file 2210 if you owe no penalty. You want to file it when your income was uneven — exactly the case with a mid- or late-year conversion. Filing lets you use the annualized method to show the IRS your income arrived late, so penalties for early quarters disappear. Skipping it when income was lumpy means accepting a penalty you could have erased.

Schedule AI — the Annualized Income Method

Schedule AI is Part of Form 2210 that matches your tax to when you actually earned the income. Instead of assuming equal income each quarter, you report income period by period (Jan–Mar, Jan–May, Jan–Aug, Jan–Dec). A Q4 conversion then only requires payment in Q4, eliminating earlier-quarter penalties. The cost is complexity — it requires quarter-by-quarter income records and more time, but tax software walks through it for you.

The Penalty Math

The penalty is interest on each quarter’s shortfall, at the federal short-term rate plus 3%, set quarterly. It is not deductible. The consequence of ignoring it is small per quarter but compounds across four periods on a large conversion. Pay on time or annualize, and you avoid it entirely.

The 2026 Estimated-Tax Deadlines

Estimated payments are due four times a year. For tax year 2026 the dates are:

Q1 (income Jan 1 – Mar 31): due April 15, 2026
Q2 (income Apr 1 – May 31): due June 15, 2026
Q3 (income Jun 1 – Aug 31): due September 15, 2026
Q4 (income Sep 1 – Dec 31): due January 15, 2027

Miss a deadline and the penalty interest starts running on that quarter’s shortfall until you pay or until April 15, 2027. Pay through IRS Direct Pay or EFTPS for instant proof of timely payment. Note Q2 covers only two months and Q4 covers four — the periods are uneven, which surprises many first-timers.

Does Your State Require Estimated Taxes Too?

Start with the federal rule above, then check your state separately — states do not automatically follow federal timing or safe-harbor rules. Most states with an income tax tax the Roth conversion as ordinary income and impose their own estimated-payment rules and penalties, often with different thresholds and due dates than the IRS.

No-income-tax states make this simple. If you live in Florida, Texas, Nevada, Washington, Wyoming, South Dakota, Alaska, Tennessee, or New Hampshire (which does not tax wages or, as of 2025, interest and dividends), there is no state tax on a Roth conversion and no state estimated payment to worry about. That answer is complete — you only manage the federal side.

Where a state diverges sharply matters. California, for example, requires 110% of prior-year tax for higher earners and front-loads its quarterly schedule (30% in Q1, 40% in Q2, 0% in Q3, 30% in Q4) — very different from the even federal schedule. What you should do: check your state revenue department’s estimated-tax page before converting, and never assume the federal safe harbor protects you at the state level.

Mistakes to Avoid

Assuming a conversion is tax-free. It is fully taxable as ordinary income; the consequence is a surprise bill of thousands of dollars.
Forgetting estimated taxes entirely. No payment means a penalty that compounds across every quarter you were short.
Using the 100% safe harbor when your AGI was over $150,000. You actually need 110%, and the gap leaves you exposed to a penalty.
Sending a late estimated payment instead of withholding. An estimated payment is credited when paid, so a December payment still triggers Q1–Q3 penalties.
Skipping Form 2210 Schedule AI after a late conversion. Without annualizing, the IRS assumes even income and charges penalties you could have erased.
Withholding tax from the conversion itself before age 59½. The withheld amount is a distribution that can trigger a 10% early-withdrawal penalty, so withhold from other funds.
Ignoring state estimated taxes. Meeting the federal safe harbor does nothing for a state with its own rules, and the state penalty stacks on top.

Do’s and Don’ts

Do check the $1,000 floor first — you may owe no estimates at all, saving you needless payments.
Do aim for the prior-year safe harbor, because it uses a known number you cannot get wrong.
Do use year-end withholding for late conversions, since it is treated as paid evenly all year.
Do keep records of when income hit each quarter, so you can annualize on Schedule AI if needed.
Do pay electronically through Direct Pay or EFTPS for dated, provable timing.
Don’t wait until April to think about the tax — the penalty already accrued across the year.
Don’t assume your state follows the IRS rules, because thresholds and schedules often differ.
Don’t withhold from the converted dollars if you are under 59½, to avoid the early-withdrawal penalty.
Don’t overpay out of fear once a safe harbor is met, since extra cash just waits for a refund.
Don’t rely on the 90% current-year test if your income is hard to predict, because a low estimate leaves you short.

Pros and Cons of Each Payment Approach

Pro of the prior-year safe harbor: it uses a fixed, known figure, so you cannot miscalculate your protection.
Pro of year-end withholding: the IRS treats it as paid evenly all year, rescuing late converters from penalties.
Pro of quarterly estimates: they spread the cash outflow and keep you current quarter by quarter.
Pro of Schedule AI annualizing: it can erase penalties on early quarters when income truly arrived late.
Pro of the $1,000 floor: it removes any obligation when your shortfall is tiny, simplifying your year.
Con of the 90% current-year test: it requires an accurate full-year estimate that is easy to get wrong.
Con of quarterly estimates: late or uneven payments still trigger per-quarter penalties.
Con of withholding from the conversion: it shrinks the Roth balance and can cause an early-withdrawal penalty under 59½.
Con of Schedule AI: it is paperwork-heavy and demands quarter-by-quarter income records.
Con of the prior-year safe harbor: it can require large payments if last year’s tax was high, even when this year’s income drops.

What to Do Next

Estimate the added tax from your conversion — multiply the amount by your top marginal rate as a quick first pass.
Find your safe-harbor target — pull last year’s total tax, then apply 100% or 110% based on your prior-year AGI.
Compare to your current withholding — if withholding already meets the target, you owe no estimates.
Cover any gap on time — pay the shortfall through quarterly estimates, or withhold it for a late conversion.
Keep your records — note when each chunk of income arrived in case you annualize on Form 2210.
Call a professional when the conversion is large, you are near IRMAA or Social Security thresholds, or your state rules are unclear. A CPA typically charges a few hundred dollars to model the conversion and set your payments — far less than a penalty plus a higher bracket.

This article is educational and not a substitute for advice from a licensed tax professional for your specific situation.

FAQs

Do I always owe estimated taxes after a Roth conversion? No. You owe nothing extra if your withholding and payments already meet a safe harbor — 90% of this year’s tax, 100% or 110% of last year’s, or a shortfall under $1,000 for the year.

How much should I pay after converting? Enough to hit one safe harbor. The easiest target is 100% of last year’s total tax (110% if your prior-year AGI topped $150,000), paid through withholding plus timely estimates.

When is the estimated payment due for a 2026 conversion? The quarter the income falls in. The 2026 due dates are April 15, June 15, September 15, 2026, and January 15, 2027, matching each income period.

Can I avoid a penalty on a December conversion? Yes. Withhold the tax directly from a year-end IRA distribution. The IRS treats withholding as paid evenly all year, so it erases penalties for earlier quarters.

Is a Roth conversion taxed as capital gains? No. The converted amount is taxed as ordinary income at your regular rates, not the lower long-term capital gains rates.

What is the safe-harbor amount if my AGI was over $150,000? 110% of last year’s tax. Once your prior-year AGI exceeds $150,000 ($75,000 if married filing separately), the 100% bar rises to 110%.

What happens if I just pay everything next April? You face a penalty. The IRS charges interest on each quarter’s shortfall from its due date, because the system requires pay-as-you-go, not one lump sum at filing.

Should I make estimated payments or change my withholding? Withholding is usually better. It counts as paid evenly across the year, while estimated payments only count when paid — a key edge for late conversions.

Do I file Form 2210 after a conversion? Only if it helps. File it to reduce a penalty using the annualized method when your income was uneven; otherwise the IRS often computes any penalty for you.

Does my state charge its own estimated-tax penalty? Usually, if it has an income tax. Most states tax the conversion and run their own estimate rules, often with different thresholds and dates; no-income-tax states charge nothing.

Can withholding from the conversion cause another penalty? Yes, under 59½. Tax withheld from the converted funds counts as a distribution and can trigger a 10% early-withdrawal penalty, so withhold from other money instead.

Is the underpayment penalty tax-deductible? No. The estimated-tax underpayment penalty is treated as interest you cannot deduct on your personal return.

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