When You Owe Taxes on a Roth Conversion

You pay taxes on a Roth conversion in the year you convert, not when you withdraw the money later

A Roth conversion moves money from a traditional IRA, SEP-IRA, SIMPLE IRA, or 401(k) into a Roth IRA. The IRS treats the amount you convert as taxable income in that same calendar year. You report it on your federal tax return for the year the conversion happened, and you owe federal income tax on it at your ordinary income tax rate. You may also owe state income tax, depending on where you live.

The tax bill arrives when you file your return the following spring, not immediately. If the amount is large enough to push you into a higher tax bracket, you pay tax at that higher rate on the converted dollars. This is why people often convert in years when their income is lower than usual—a job loss, retirement, or a year with unusually small business income can create a lower-tax-rate window.

The money you convert has already been taxed once (if it came from a traditional IRA with after-tax contributions) or not at all (if it came from pre-tax contributions). The conversion tax applies only to the pre-tax portion. This distinction matters because the IRS has a rule called the pro-rata rule that can make conversions more expensive than they appear.

Key Takeaways

• You owe income tax on the converted amount in the year you convert, reported on that year's tax return and due when you file the following spring.
• The tax rate you pay depends on your total income that year—a large conversion can push you into a higher bracket and increase the tax on all your income.
• If you have other traditional IRAs with pre-tax money in them, the pro-rata rule requires you to count that money when calculating how much of your conversion is taxable.
• You can pay the tax from outside the Roth account (leaving more money to grow tax-free) or from the conversion itself (which reduces what actually ends up in the Roth).
• Some conversions trigger Medicare premium increases the following year because the IRS counts conversion income when calculating your Modified Adjusted Gross Income.

How the pro-rata rule increases your tax bill

The pro-rata rule is the reason a Roth conversion can cost more than the simple math suggests. If you have $50,000 in a traditional IRA (all pre-tax money) and you convert $20,000 to a Roth, you might think you owe tax on $20,000. But if you also have a SEP-IRA with $30,000 in pre-tax contributions, the IRS treats all your traditional IRAs as one pool.

The rule works like this: add up all your traditional, SEP, and SIMPLE IRAs. Calculate what percentage is pre-tax money. Apply that percentage to the amount you convert. That is the taxable portion. In the example above, you have $80,000 total across both accounts, and $80,000 is pre-tax. So 100 percent of your $20,000 conversion is taxable. If instead you had $30,000 in after-tax contributions sitting in one of those accounts, only 62.5 percent of the conversion would be taxable ($50,000 pre-tax divided by $80,000 total).

The pro-rata rule applies to all your traditional IRAs combined—it does not matter which account you convert from. This is why people with multiple IRAs sometimes consolidate them before converting, or why they move pre-tax money into a 401(k) first (401(k)s are not included in the pro-rata calculation).

Paying the tax from your bank account versus from the conversion itself

You have two ways to handle the tax bill. You can pay it from money outside the Roth account—from your checking account, savings, or another source. This leaves the full converted amount in the Roth to grow tax-free. Or you can instruct the financial institution to withhold the tax from the conversion itself, which means less money actually ends up in the Roth.

Paying from outside is almost always better if you can afford it. If you convert $20,000 and owe $5,000 in tax, paying from your bank account leaves $20,000 in the Roth. Paying from the conversion itself means only $15,000 goes into the Roth, and you have lost the tax-free growth on that $5,000 forever. The only reason to withhold from the conversion is if you do not have cash on hand to pay the tax separately.

If you do withhold tax from the conversion, the IRS still counts the full converted amount as income on your tax return. You report the gross conversion amount, not the net amount that landed in the Roth. The withholding is just a prepayment toward your tax bill.

How conversion income affects Medicare premiums the following year

A Roth conversion can increase your Medicare premiums if you are already enrolled in Medicare or will be soon. Medicare uses a figure called Modified Adjusted Gross Income (MAGI) to determine your Part B and Part D premiums. A conversion adds to your MAGI for that year, which can push you into a higher premium bracket.

The premium increase takes effect two years after the conversion. If you convert in 2024, your 2024 MAGI (including the conversion) determines your 2026 Medicare premiums. This two-year lag means you might not see the impact immediately, but it is real. Someone converting $100,000 in the year they turn 65 could pay significantly higher premiums for years afterward.

You can request a Medicare Income-Related Monthly Adjustment Amount (IRMAA) appeal if a one-time event like a conversion caused your income to spike. Medicare will review the appeal and may lower your premiums if the conversion was temporary and not representative of your ongoing income. You file the appeal with Social Security using Form SSA-44.

Timing your conversion to minimize your tax bracket

The year you convert matters because your total income that year determines your tax rate. If you convert $50,000 when your other income is $200,000, you pay tax at a higher rate than if you convert the same $50,000 when your other income is $50,000. This is why people often plan conversions around life events that lower their income.

A year you retire before Social Security starts is a common conversion window. A year you take a sabbatical or have a business loss can work too. Some people convert in the year they turn 70½ and must take a required minimum distribution (RMD) anyway—the RMD counts as income regardless, so they might as well convert additional money at the same tax rate.

You cannot undo a conversion to avoid the tax bill. Before 2018, you could reverse a conversion (called a recharacterization) if the market dropped and you regretted it. That option no longer exists. Once you convert, the tax is owed. This is why some people do smaller conversions over several years rather than one large conversion—it spreads the tax impact across multiple years and gives them more control over their tax bracket each year.

State income tax on conversions

Federal income tax is only part of the bill. Most states tax Roth conversions as ordinary income in the year you convert. A few states do not tax retirement income at all—including Florida, Nevada, South Dakota, Tennessee, Texas, Washington, and Wyoming. If you live in one of these states, you owe federal tax on the conversion but no state tax.

If you live in a state with income tax, the conversion is taxed at your state rate in addition to your federal rate. Some states have special rules for retirees or for income over a certain threshold, so the effective state rate can vary. A few states tax only certain types of retirement income, so the rules depend on which account you are converting from.

This is one reason some people move to a no-income-tax state before converting large amounts. The tax savings can be substantial. If you are considering a move, timing the conversion after you establish residency in the new state can save you state tax entirely.

What happens if you cannot pay the tax bill by April 15

If you owe tax on a conversion and cannot pay it when you file your return, you can request a payment plan from the IRS. The IRS offers short-term payment plans (up to 180 days) at no cost, and long-term installment agreements that charge interest and a setup fee. The longer you take to pay, the more interest accrues.

You must file your tax return on time even if you cannot pay the full amount. Filing late triggers additional penalties on top of the interest. If you file on time but pay late, you owe interest and a failure-to-pay penalty, but the penalties are smaller than if you file late.

Some people pay the conversion tax from a home equity line of credit or a personal loan to avoid the IRS payment plan fees. Others delay the conversion itself until a year when they know they will have the cash to pay the tax. There is no penalty for not converting—the decision to convert is entirely yours.

Frequently Asked Questions

Do I have to pay the tax all at once, or can I pay it over time?

You can set up an IRS payment plan if you cannot pay the full amount by April 15. Short-term plans (up to 180 days) are free. Longer plans charge interest and a setup fee. You must file your return on time regardless of whether you can pay immediately.

What if I convert in December—do I owe tax that same year or the next year?

You owe tax in the year you convert, regardless of when in the year it happens. A December conversion is taxable in that same calendar year. You report it on your tax return filed the following spring, and the tax is due April 15 of that year.

Can I convert just the after-tax money in my IRA to avoid taxes?

No. The pro-rata rule requires you to treat all your traditional IRAs as one account. If you have both pre-tax and after-tax money across your IRAs, a percentage of any conversion is taxable based on the ratio of pre-tax to total. You cannot cherry-pick only the after-tax portion.

Does a Roth conversion count as income for Social Security taxation?

Yes. Conversion income is added to your Modified Adjusted Gross Income, which can increase the portion of your Social Security benefits that are taxable. This is separate from the Medicare MAGI impact and can affect your overall tax bill in the conversion year.

What if the market drops after I convert—can I get the tax back?

No. You cannot reverse a conversion to recover the tax you paid. You owe tax on the amount you converted, regardless of what that money is worth later. This is why some people convert smaller amounts or wait for market dips before converting, to minimize the value they are converting at that moment.