What a Roth conversion is

A Roth conversion is when you move money from a traditional retirement account — usually a traditional IRA or a 401(k) — into a Roth IRA. You pay income tax on the amount you convert in that tax year, but once the money is in the Roth, it grows tax-free and you can withdraw it tax-free in retirement.

The trade-off is straightforward: you pay taxes now instead of later. You're converting pre-tax dollars (which reduced your taxable income when you contributed them) into after-tax dollars (which won't be taxed again when you take them out). This only makes sense if you believe your tax rate will be higher in retirement than it is today, or if you want to reduce the size of your traditional accounts for other reasons.

Unlike a regular contribution to a Roth IRA, there is no income limit on who can do a conversion. You can have a very high income and still convert. The only limit is how much money you actually have in traditional accounts to convert.

Key Takeaways

  • A Roth conversion moves money from a traditional IRA or 401(k) into a Roth IRA, and you pay income tax on the converted amount in that year.
  • After conversion, the money grows tax-free and withdrawals in retirement are tax-free, unlike traditional account withdrawals.
  • There is no income limit on conversions, even if you earn too much to contribute directly to a Roth IRA.
  • You must have a Roth IRA open before you convert; you cannot convert directly from a 401(k) to a Roth without an IRA in between.
  • The tax bill from a conversion is due when you file your tax return for that year, not when you do the conversion itself.

How the conversion process works

The actual mechanics are straightforward. You contact the financial institution that holds your traditional IRA or 401(k) and tell them you want to convert a specific amount to a Roth IRA. They move the money from one account to the other. Some institutions let you do this online; others require a form or a phone call.

If you're converting from a 401(k), you typically have to roll it to a traditional IRA first, then convert from the IRA to the Roth. A few employers allow direct conversions from 401(k) to Roth, but this is less common. Check with your plan administrator to see if your plan allows it.

The conversion itself is not a taxable event at the moment you do it. The tax bill arrives later, when you file your tax return. Your financial institution will send you a Form 1099-R showing the conversion amount, and you'll report it on your tax return. The IRS treats the converted amount as ordinary income for that year.

When the tax bill is due and how much it costs

You owe income tax on the full amount you convert, calculated at your ordinary income tax rate for that year. If you convert $50,000 and your tax bracket is 24%, you owe roughly $12,000 in federal income tax. Some states also tax conversions, so your total bill could be higher.

The tax is due when you file your tax return the following spring. You don't pay it when you do the conversion. This timing matters: if you convert in December, you have until April to figure out how to pay the bill, but the money is already in your Roth account.

Many people pay the tax from money outside their retirement accounts so they don't have to withdraw from the Roth to cover the bill. If you withdraw from the Roth to pay the tax, you're reducing the benefit of the conversion and may trigger additional taxes.

Why people convert and when it makes sense

The main reason to convert is tax planning. If you expect to be in a higher tax bracket in retirement — or if tax rates rise in the future — converting now at a lower rate saves you money over time. You're locking in today's tax rate instead of paying whatever rate applies when you withdraw the money later.

A second reason is to reduce your required minimum distributions (RMDs). Traditional IRAs force you to withdraw a certain amount each year starting at age 73, and those withdrawals are taxed as ordinary income. By converting money to a Roth, you shrink your traditional account balance, which lowers your future RMDs. Roth IRAs have no RMDs during your lifetime, so the money can keep growing untouched.

A third reason is to leave more tax-information programs to heirs. Roth accounts pass to beneficiaries with a tax-free growth period, whereas traditional accounts are taxed when beneficiaries withdraw. If leaving money to your children or grandchildren is a goal, a Roth conversion can be part of that strategy.

Conversions make less sense if you're in a very high tax bracket this year, or if you expect to be in a lower bracket in retirement. They also don't help if you need the converted money soon — the tax bill can be large, and paying it from the Roth defeats the purpose.

The pro-rata rule and why it matters

If you have both traditional and Roth IRAs, the pro-rata rule affects how much of your conversion is taxed. The IRS treats all your traditional IRAs as one account for tax purposes, even if they're at different banks. When you convert, you can't pick and choose which dollars are pre-tax and which are after-tax.

Here's an example: suppose you have $100,000 in a traditional IRA (all pre-tax) and $20,000 in a Roth IRA. You want to convert $10,000 from the traditional IRA. The IRS says that 83% of your total IRA balance is pre-tax ($100,000 out of $120,000), so 83% of your $10,000 conversion — about $8,300 — is taxable. You can't convert just the after-tax portion and avoid the tax.

This rule is one reason some people open a Solo 401(k) or roll traditional IRAs into their employer's 401(k) plan before converting. Those accounts are not subject to the pro-rata rule, so you can separate pre-tax and after-tax money more cleanly. But this strategy requires that your employer's plan allows rollovers in, which not all do.

Conversions and Medicare premiums

A Roth conversion increases your taxable income for that year, which can affect your Medicare premiums if you're on Medicare. Medicare uses your modified adjusted gross income (MAGI) from two years prior to set your premiums. A large conversion can push you into a higher income bracket and raise what you pay for Part B and Part D coverage.

The premium increase is temporary — it applies only to the year your income is higher — but it's a real cost to factor in. If you're close to a Medicare income threshold, a conversion might bump you up and cost you hundreds or thousands in extra premiums that year. Some people spread conversions over multiple years to stay below the threshold.

Backdoor Roth conversions and the income limit workaround

A backdoor Roth is a strategy where you contribute money to a traditional IRA (which has no income limit) and then when ready convert it to a Roth. This lets high-income earners get money into a Roth even though they can't contribute directly due to income limits.

The backdoor works because conversions have no income limit, only contributions do. You contribute $7,000 to a traditional IRA, it sits there for a day or two, then you convert it to a Roth. You owe tax only on any earnings that accumulated in those few days, which is usually zero or a few dollars.

The pro-rata rule still applies to backdoor conversions. If you have existing pre-tax money in any traditional IRA, the conversion becomes partially taxable. This is why people with high incomes sometimes roll old 401(k)s into their current employer's plan before doing a backdoor conversion — to get the pre-tax money out of the IRA system.

Frequently Asked Questions

Can I undo a Roth conversion if I change my mind?

You used to be able to "recharacterize" a conversion and move the money back, but that option ended in 2018. Now, once you convert, the conversion is permanent. You can't reverse it. This is why some people do smaller conversions or spread them over multiple years — to avoid locking in a large tax bill if circumstances change.

Do I have to convert my entire traditional IRA at once?

No. You can convert any amount you want, from a small portion to the whole account. Many people convert in chunks over several years to spread out the tax bill and stay in a lower bracket each year. There's no rule requiring you to convert everything at once.

What happens if I don't have the money to pay the tax bill?

You can pay the tax from any source — savings, a loan, or even a withdrawal from another account. If you withdraw from the Roth itself to pay the tax, you're reducing the benefit of the conversion. Some people time conversions for years when they have extra income or a bonus to cover the tax bill.

Can I convert a 401(k) directly to a Roth without opening an IRA?

Some employer plans allow direct conversions from 401(k) to Roth 401(k), but most require you to roll to a traditional IRA first. Check with your plan administrator or HR department to see if your plan supports direct conversions. If not, you'll need to open a traditional IRA as an intermediate step.

Does a Roth conversion affect my Social Security benefits?

Roth conversions count as taxable income and can affect how much of your Social Security is taxed, similar to other income. If you're close to the threshold where Social Security becomes taxable, a large conversion might push you over. This is another reason to consider spreading conversions across multiple years.