You owe income tax on the converted amount in the year you convert

When you convert money from a traditional IRA to a Roth IRA, the IRS treats that conversion as income. You must report it on your tax return for the year the conversion happened, and you'll owe ordinary income tax on the full amount you moved — not just the earnings, but the entire converted balance.

The tax bill is separate from any penalty. You don't pay it through the Roth conversion itself. Instead, you report the conversion on your tax return, calculate your new tax liability, and pay it like any other income tax — either through withholding adjustments, estimated tax payments, or when you file.

This is why conversion strategy matters: converting a large amount in a single year can push you into a higher tax bracket and cost significantly more than spreading conversions across multiple years.

Key Takeaways

  • Report the full converted amount as income on your tax return for the year the conversion occurred, using Form 8606 if you have pre-tax IRA balances.
  • You owe ordinary income tax on the conversion at your marginal tax rate for that year, which can be higher if the conversion pushes you into a new bracket.
  • The IRS sends you a Form 1099-R showing the conversion; your brokerage also reports it, so misreporting is easily caught.
  • You can pay the tax through withholding, estimated tax payments during the year, or as part of your annual tax bill when you file.
  • If you convert in December, you still report and pay tax in that same calendar year, even if the funds don't settle until January.

Form 8606 and reporting the conversion to the IRS

You report a Roth conversion using Form 8606, which is filed with your main tax return (Form 1040). This form tells the IRS how much you converted and calculates how much of that conversion is taxable.

Form 8606 is required if you have any pre-tax IRA money — including traditional IRAs, SEP IRAs, or SIMPLE IRAs — at the end of the year you convert. The form uses the "pro-rata rule," which means you can't convert only the after-tax portion of your IRA and avoid tax on the rest. If you have $80,000 in pre-tax money and $20,000 in after-tax contributions across all your IRAs, 80 percent of any conversion is taxable.

Your brokerage will send you a Form 1099-R showing the conversion amount. This goes to the IRS automatically, so if you don't file Form 8606 or report the conversion, the IRS will notice the mismatch and may assess additional tax and penalties.

How much tax you actually owe depends on your total income

The conversion is taxed at your marginal tax rate — the rate you pay on your last dollar of income that year. If you earn $60,000 as a single filer and convert $20,000, that $20,000 is taxed at the rate for income between $60,000 and $80,000, not at the lowest bracket rate.

This is why the timing and size of conversions matter. Converting $50,000 when you're already in the 24 percent bracket costs more than converting $50,000 in a year when you're in the 12 percent bracket. Some people convert in years when they take a sabbatical, have lower business income, or are between jobs specifically to use a lower bracket.

Your conversion can also affect other tax items: it may reduce the amount of deductible IRA contributions you can make that year, push you into a higher Medicare premium bracket (IRMAA), or affect how much of your Social Security is taxable if you're retired. A tax professional can model these effects before you convert.

Paying the tax through withholding or estimated payments

You have three ways to pay the tax on a conversion: adjust your withholding, make estimated tax payments, or pay it all when you file your return.

If you have a job with W-2 withholding, you can increase the amount withheld from your paycheck to cover the conversion tax. Use Form W-4 to tell your employer to withhold more. This is the simplest method if you have steady employment income.

If you're self-employed or have no withholding, you can make estimated tax payments to the IRS in quarterly installments (April 15, June 15, September 15, and January 15). You calculate what you expect to owe for the year, divide it by four, and send payments to the IRS. Underpaying estimated taxes can result in a penalty, even if you pay the full amount when you file.

You can also simply pay the full tax bill when you file your return in April, but this works only if you won't owe a penalty for underpayment. The IRS allows this if your withholding and estimated payments equal at least 90 percent of your current year tax or 100 percent of your prior year tax (110 percent if your prior year income was over $150,000).

The pro-rata rule and after-tax IRA money

The pro-rata rule is the biggest tax trap in conversions. It says you can't cherry-pick only the after-tax money in your IRAs and convert that tax-free. Instead, the IRS treats all your IRAs as one pool and taxes conversions proportionally.

Here's the math: if you have $100,000 in pre-tax IRAs and $25,000 in after-tax contributions (non-deductible IRA contributions you've already paid tax on), your total IRA balance is $125,000. If you convert $50,000, the IRS says 80 percent of it ($40,000) comes from pre-tax money and is taxable, and 20 percent ($10,000) comes from after-tax money and is not taxable.

This rule applies across all your IRAs, including rollover IRAs from old 401(k)s. If you have a large 401(k) balance and a small after-tax IRA, converting the after-tax IRA still triggers tax on most of the conversion because of the pro-rata calculation. Some people roll their 401(k) into a new employer plan to remove it from the pro-rata calculation, then convert their IRA separately.

Reporting the conversion in the year it happens, not when it settles

The conversion is taxable in the calendar year you initiate it, not the year the money settles in your Roth account. If you convert on December 28 and the transfer completes on January 5, you report it on your current-year return, not next year's.

This matters for year-end planning. You can't avoid a year's tax by converting in late December and waiting until January to complete the transfer. The IRS date is the date you instruct the transfer, not the settlement date.

Your brokerage will show the conversion date on the Form 1099-R they send you, and that's the date you use for your tax return.

What happens if you can't pay the tax bill

If you convert but can't afford to pay the tax, you still owe it. The conversion doesn't reverse just because you didn't pay. You can set up a payment plan with the IRS (Form 9465) to pay in installments, but you'll owe interest and penalties on the unpaid balance.

Some people make the mistake of taking the tax money out of the Roth account after converting. This creates a second problem: that withdrawal may be subject to the five-year rule and early withdrawal penalties if you're under 59½. It's better to pay the tax from other sources — a checking account, a bonus, or a side income — and leave the converted money in the Roth to grow.

If you realize after converting that you can't afford the tax, you can request a recharacterization (moving the money back to a traditional IRA) only if your brokerage still offers it. Most brokerages stopped offering recharacterizations after 2017, so this option is rarely available now. Check with your brokerage before converting if this is a concern.

Frequently Asked Questions

Do I have to pay the tax in the same year I convert?

You must report the conversion and owe the tax in the year it happens, but you can pay it through withholding adjustments, estimated payments, or when you file your return. You don't have to pay it immediately, but if you underpay, you'll owe penalties on the unpaid amount.

What if I have both pre-tax and after-tax money in my IRA?

The pro-rata rule means you can't convert only the after-tax portion. If 80 percent of your total IRA balance is pre-tax, then 80 percent of any conversion is taxable. You report the taxable and non-taxable portions on Form 8606.

Can I deduct the conversion as a loss on my taxes?

No. A Roth conversion is not deductible. You report the full converted amount as income. If the account loses value after conversion, you can't claim a loss related to the conversion itself.

What if I made a mistake on Form 8606?

File an amended return using Form 1040-X for the year of the conversion. Attach a corrected Form 8606. If you underreported the taxable amount, you'll owe additional tax and interest. If you overreported, you may get a refund.

Does the conversion affect my Medicare premiums or Social Security tax?

Yes. The conversion counts as income for Medicare premium calculations (IRMAA) and can affect how much of your Social Security is taxable. These effects vary by your total income and filing status, so it's worth modeling before you convert.