How a Roth IRA Conversion Works and Why People Do It

What happens when you convert to a Roth IRA

A Roth IRA conversion means moving money from a traditional IRA, SEP IRA, straightforward IRA, or a workplace retirement plan like a 401(k) into a Roth IRA. You pay income tax on the amount you move in the year you convert it. After that, the money grows tax-free, and you can withdraw it tax-free in retirement — unlike a traditional IRA, where withdrawals are taxed as ordinary income.

The IRS allows anyone with earned income to convert, regardless of how much money they make. There is no income limit that blocks you from converting, though there are income limits on contributing directly to a Roth IRA each year. A conversion is a one-time event: you decide to move the money, you pay the tax bill, and the conversion is complete.

The conversion itself is straightforward. You contact the financial institution holding your traditional IRA or 401(k) and ask them to transfer the funds to a Roth IRA. The institution handles the paperwork. You report the conversion on your tax return for that year, and you owe tax on the full amount converted (minus any basis — money you contributed with after-tax dollars).

Key Takeaways

A Roth conversion moves money from a traditional or workplace retirement account into a Roth IRA, and you pay income tax on the amount in the year you convert.
After conversion, the money grows tax-free and you can withdraw it tax-free in retirement, unlike traditional IRAs where all withdrawals are taxed.
There is no income limit on who can convert, though there are income limits on direct Roth contributions each year.
You report the conversion on Form 8606 when you file your tax return, and the tax owed depends on your total income that year.
A conversion is permanent — you cannot undo it, though the IRS allows a small window to recharacterize (move money back) in limited situations.

Why the tax bill matters more than the conversion itself

The reason people hesitate over conversions is the tax bill. If you convert $50,000, you owe federal income tax on $50,000 in that year. The tax rate depends on your tax bracket — it could be 22 percent, 24 percent, 32 percent, or higher, depending on your total income that year and your filing status. That means a $50,000 conversion could cost you $11,000 to $16,000 in federal tax alone, plus any state income tax.

People convert when they expect to be in a lower tax bracket than they will be in retirement. A common scenario: you retire before age 65 and have a year with unusually low income. You convert during that low-income year, pay tax at a lower rate, and then let the money grow tax-free for decades. Another scenario: you expect tax rates to rise in the future, so you pay tax now at today's rates rather than higher rates later.

The conversion does not have to happen all at once. You can convert part of your traditional IRA one year and part another year, spreading the tax bill across multiple years. This is called a partial conversion or a ladder conversion if you do it systematically over several years.

The pro-rata rule and why it complicates conversions

If you have both a traditional IRA with pre-tax money and a traditional IRA with after-tax money (called basis), the IRS treats all your traditional IRAs as one pool for conversion purposes. This is the pro-rata rule. It means you cannot convert only the after-tax portion and avoid tax on the pre-tax portion.

Here is how it works: suppose you have $100,000 in traditional IRAs total — $80,000 pre-tax and $20,000 after-tax basis. You want to convert $20,000 (the after-tax part) to avoid a tax bill. The IRS says no. When you convert $20,000, the IRS treats it as 80 percent pre-tax and 20 percent after-tax, based on your total balance. So you owe tax on $16,000 of the $20,000 you converted.

This rule catches many people off guard. If you have a workplace 401(k) with pre-tax money and a separate traditional IRA with after-tax contributions, the pro-rata rule still applies — the IRS counts both accounts together. The workaround is to roll the 401(k) into the traditional IRA first, which does not trigger the pro-rata rule, but that combines the accounts and makes the problem worse. Some people roll a 401(k) into a separate Roth 401(k) instead, which sidesteps the pro-rata rule entirely, though not all employers offer that option.

When you can undo a conversion

You cannot straightforward change your mind and reverse a conversion. Once the money is in the Roth IRA, it stays there. However, the IRS allows recharacterization in narrow circumstances — you can move the money back to a traditional IRA if the value has dropped significantly and you file your tax return on time (including extensions).

Recharacterization is useful if you convert $50,000 and the market drops and your Roth IRA is now worth $35,000. You can move it back to a traditional IRA, undo the conversion on your tax return, and avoid paying tax on the $15,000 loss. Then you can convert again later if you want.

The important date to recharacterize is the tax-filing important date for that year, including extensions. If you file your return on October 15 (with an extension), you have until that date to recharacterize. After that, the conversion is permanent.

How conversions affect your taxes that year

A conversion increases your taxable income for the year you convert. This can push you into a higher tax bracket, which means you pay tax on the conversion amount at a higher rate than you might expect. It can also trigger other tax consequences: your Medicare premiums may increase if you are on Medicare, because they are based on your income from two years prior. Your Social Security benefits may become partially taxable if you are receiving them. Your child tax credits or education credits may shrink.

This is why people often plan conversions carefully. A financial advisor or tax professional can model out the tax impact before you convert. They calculate what your total income will be that year, what tax bracket you will land in, and what other tax consequences might follow. Then you decide whether the conversion makes sense.

You report the conversion on Form 8606 when you file your federal tax return. This form tells the IRS how much you converted, how much basis (after-tax money) you had, and how much of the conversion is taxable. If you do not file Form 8606, the IRS may assess additional tax and penalties.

Roth conversions and required minimum distributions

A Roth IRA has no required minimum distributions during your lifetime. A traditional IRA does — you must start withdrawing at age 73 (as of 2023; this age changes under current law). If you have a large traditional IRA and do not need the money, the required withdrawals force you to take taxable income you do not want.

Converting a traditional IRA to a Roth eliminates those future required withdrawals. The money can stay in the Roth and grow tax-free for as long as you live. This is one reason people convert late in their working years or early in retirement: they want to avoid large forced withdrawals later.

However, a conversion itself counts as income that year. So converting a large balance to avoid future required distributions means taking a large income hit now. The math only works if you are in a low-income year or if you expect tax rates to be much higher in the future.

Frequently Asked Questions

Can I convert a 401(k) directly to a Roth IRA?

Yes, but only if your 401(k) plan allows it. Not all plans do. You can also roll the 401(k) to a traditional IRA first, then convert the IRA to a Roth. The second route takes an extra step but works if your plan does not allow direct conversions. Check with your plan administrator or your employer's benefits office to see what your plan allows.

What if I convert and then my income is higher than I expected?

You still owe tax on the full conversion amount. The tax bill does not change based on what happens after you convert. If you are worried about a surprise income spike, you can recharacterize (move the money back) before the tax-filing important date, which undoes the conversion and the tax bill. After the important date, you are locked in.

Do I have to convert all my traditional IRAs at once?

No. You can convert some and leave the rest in the traditional IRA. However, the pro-rata rule still applies to the amount you convert — it is calculated based on your total balance across all traditional IRAs, not just the one you are converting from. You can spread conversions across multiple years to manage the tax bill.

Will a conversion affect my Social Security benefits?

Possibly. Social Security benefits become partially taxable if your combined income (adjusted gross income plus nontaxable interest plus half your Social Security) exceeds certain thresholds. A conversion increases your income that year, which could push you over the threshold and make more of your benefits taxable. The impact depends on your specific situation and income level.

Can I convert a Roth IRA back to a traditional IRA?

No. Recharacterization only works in one direction — moving money from a Roth back to a traditional IRA to undo a conversion. You cannot move money from a Roth to a traditional IRA for any other reason. Once money is in a Roth, it stays there or comes out as a withdrawal.

This guide is for general information only and is not medical, financial, legal, or other professional advice. For decisions specific to your situation, consult a qualified professional. See our Editorial Policy.