How the IRS Taxes Your Roth Conversion

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

When you move money from a traditional IRA, SEP-IRA, or SIMPLE IRA into a Roth IRA, the IRS treats that transfer as taxable income. You report it on your federal tax return for the year the conversion happens. The tax bill is based on how much you converted, not on how much you contributed over the years or how much has grown.

The conversion itself does not trigger a 10% early withdrawal penalty, even if you are under 59½. But you will owe ordinary income tax on the full amount converted, calculated at your marginal tax rate for that year. If you convert $50,000 and your top tax bracket is 24%, you will owe roughly $12,000 in federal income tax (plus any state income tax, depending on where you live).

Key Takeaways

• The entire amount you convert is added to your taxable income for that year, taxed at your ordinary income tax rate.
• Pre-tax contributions and earnings in your traditional IRA are always taxable when converted; after-tax contributions are not.
• The "pro-rata rule" means you cannot convert only the after-tax portion if you have other traditional IRAs with pre-tax money — the IRS taxes a proportional share of the whole.
• You must report the conversion on Form 8606 and pay the tax by April 15 of the following year, or request an extension.
• State income tax applies to conversions in most states, and a few states tax Roth conversions differently than the federal government does.

How the pro-rata rule affects what you owe

If you have multiple traditional IRAs, SEP-IRAs, or SIMPLE IRAs, the IRS applies the pro-rata rule to determine how much of your conversion is taxable. You cannot simply convert the after-tax contributions and leave the pre-tax money behind. Instead, the IRS looks at the total value of all your IRAs combined on December 31 of the conversion year, calculates what percentage is pre-tax, and applies that percentage to your conversion.

Suppose you have $100,000 in a traditional IRA (all pre-tax contributions and earnings) and $20,000 in a SEP-IRA (also pre-tax). You also have $30,000 in after-tax contributions sitting in a separate traditional IRA. Your total IRA balance is $150,000, of which $130,000 is pre-tax and $20,000 is after-tax. That means 86.7% of any conversion is taxable. If you convert $30,000, roughly $26,000 is taxable income and $4,000 is not.

The pro-rata rule applies across all IRAs you own, regardless of which account you convert from. It does not matter if you convert from the account holding after-tax money — the rule still applies to your entire IRA universe. This is one reason people sometimes move pre-tax IRAs into their employer 401(k) plan before converting: if you move the pre-tax balance out of the IRA system, it no longer counts toward the pro-rata calculation.

Reporting the conversion on your tax return

You report a Roth conversion using Form 8606, which you file with your federal tax return. The form asks for the total value of all your IRAs on December 31, the amount you converted, and how much of that conversion is taxable versus non-taxable. You also report the conversion amount on your Form 1040 as additional income.

If you do not file Form 8606, the IRS may assume the entire conversion is taxable, even if part of it came from after-tax contributions. Filing the form correctly protects you by documenting which dollars were after-tax and therefore not subject to income tax again. Keep records of all contributions to your IRAs — especially after-tax contributions — because you will need them to complete the form accurately.

The deadline to report the conversion is the same as your tax return deadline: April 15 of the year following the conversion (or October 15 if you file an extension). You cannot amend a conversion after the tax year ends, so the year you convert is the year you pay tax on it.

State income tax on conversions

Most states that have an income tax will tax your Roth conversion as ordinary income, just as the federal government does. However, a handful of states treat Roth conversions differently. Some states do not tax retirement income at all, which can make a conversion more attractive if you live there. Others tax conversions but not other retirement distributions, creating an unusual situation where converting is more expensive than taking a regular withdrawal.

Illinois, Mississippi, and Pennsylvania do not tax retirement income, including Roth conversions. South Dakota, Tennessee, Texas, Washington, and Wyoming have no state income tax at all. If you live in one of these states, you avoid state tax on the conversion. If you live elsewhere, check your state's rules or consult a tax professional, because state treatment varies and can significantly affect the total cost of converting.

Timing the conversion to manage your tax bracket

Because the conversion is taxed at your ordinary income tax rate, the year you convert matters. If you have a year with unusually low income — perhaps you took unpaid leave, retired mid-year, or had a business loss — converting in that year may push you into a lower tax bracket than you would occupy in a normal year.

Conversions are also useful after a market downturn, when your IRA balance has fallen. You convert the same number of dollars but pay tax on a smaller amount, then the account grows tax-free inside the Roth. This is sometimes called a "down-market conversion" and can be more tax-efficient than converting when balances are high.

You can also split a conversion across multiple years. There is no rule requiring you to convert all at once. Some people convert a fixed amount each year to spread the tax bill and stay in a consistent bracket, while others convert large amounts in low-income years and nothing in high-income years.

What happens if you undo a conversion

You can reverse a Roth conversion by moving the money back to a traditional IRA. This is called a recharacterization. You must complete the recharacterization by the tax return deadline for the year of the conversion (including extensions). If you recharacterize, you do not owe tax on the converted amount, and you file an amended Form 8606 to report it.

Recharacterization is useful if the market drops after you convert and you want to avoid paying tax on money that has lost value. You move the funds back, file the amended form, and the conversion is treated as if it never happened. You can then convert again in a later year when conditions are more favorable.

Frequently Asked Questions

Do I owe the conversion tax immediately, or can I pay it later?

You report the tax on your return due April 15 of the following year (or October 15 with an extension). You can pay the tax then, or if you owe other taxes, the IRS will apply your payment to your total bill. You cannot defer payment beyond the tax deadline without facing penalties and interest.

What if I convert and then the market drops — do I still owe tax on the original amount?

Yes, you owe tax on the amount you converted, not on what it is worth later. If you convert $50,000 and it falls to $40,000, you still owe tax on $50,000. This is why some people recharacterize after a market drop — to undo the conversion and avoid the tax bill on the now-smaller balance.

Can I use money from the Roth conversion to pay the tax bill?

You can, but it is usually not recommended. If you take money out of the Roth to pay the tax, you reduce the amount growing tax-free. Some people instead convert a smaller amount and pay the tax from other savings, so more money stays in the Roth account.

Does a conversion count toward the income limits for other tax benefits?

Yes. The conversion amount is added to your modified adjusted gross income (MAGI), which can affect your may be able to access for deductions, credits, and other benefits. A large conversion might push you over the income limit for the child tax credit, education credits, or the ability to deduct traditional IRA contributions.

What if I have a 401(k) and a traditional IRA — does the pro-rata rule apply?

No. The pro-rata rule applies only to IRAs (traditional, SEP, and SIMPLE). A 401(k) is separate, so you can move pre-tax money from your 401(k) into a Roth 401(k) without triggering the pro-rata rule on your IRAs. This is one reason people sometimes roll a 401(k) into a traditional IRA before converting — but doing so brings the 401(k) money into the pro-rata calculation.