You owe income tax on the converted amount in the year you convert, not when you withdraw it later

A Roth conversion moves money from a traditional IRA (or similar pre-tax account) into a Roth IRA. The IRS treats that moved money as income in the year you convert it. You report it on your tax return for that year and pay tax on it then — usually by April 15 of the following year, or when you file. The tax bill is separate from any penalties or restrictions on withdrawals; it is purely about income tax owed on the amount converted.

The amount you owe depends on your tax bracket that year and how much you converted. If you converted $50,000 and you are in the 24% federal tax bracket, you would owe roughly $12,000 in federal tax on that conversion (plus any state income tax, if your state has it). That tax is due when you file your return, not when you move the money.

Key Takeaways

  • You report the converted amount as taxable income on your tax return for the year you convert, and you owe tax by the filing deadline of that year.
  • The tax you owe is based on your total income that year and your tax bracket, not a flat rate on the conversion.
  • You can pay the tax from the converted funds themselves, from other savings, or through increased withholding on paychecks — the IRS does not care where the money comes from.
  • If you do not pay the tax by the deadline, you owe interest and penalties on top of the unpaid amount.
  • Some people convert in years when their income is lower (like after retirement or a job loss) to reduce the tax bill.

How the IRS calculates your tax bill on a conversion

The IRS adds the converted amount to your other income for that year. If you earned $60,000 in salary and converted $50,000, your taxable income is $110,000. Your tax bracket is determined by that total, not by the conversion alone. This means a large conversion can push you into a higher tax bracket, raising the rate you pay on both the conversion and your other income.

If you have pre-tax contributions in any traditional IRA, SEP IRA, or SIMPLE IRA, the IRS uses a "pro-rata rule" that complicates the math. You cannot convert only the after-tax portion and leave the pre-tax portion behind. Instead, the IRS treats all your IRAs as one pool and taxes you on a percentage of the conversion based on how much of that pool is pre-tax money. This is one reason people sometimes move pre-tax IRAs into a 401(k) before converting — it removes them from the pro-rata calculation.

When you actually pay the tax: filing deadline or estimated payments

The standard way to pay is when you file your tax return. You report the conversion on Form 8606, add it to your income, and pay the resulting tax by April 15 (or October 15 if you file an extension). The IRS does not require you to pay before then.

However, if the tax bill is large enough to create a gap between what you have already paid in (through withholding or estimated payments) and what you will owe, the IRS may expect quarterly estimated tax payments. If you do not make them, you can owe a penalty for underpayment even if you pay the full amount by April 15. The penalty is small — usually a few hundred dollars — but it adds up if you convert a large amount and do not adjust your withholding or make estimated payments.

To avoid the penalty, you can increase withholding on a paycheck (if you have employment income) or make quarterly estimated payments using Form 1040-ES. Many people simply pay the tax from their conversion funds or other savings when they file their return and accept the small penalty if one applies.

Paying tax from the conversion itself versus other money

You can pay the tax bill from anywhere: the converted funds, other savings, a paycheck, a loan, or any other source. The IRS does not care. However, this choice has real consequences for your retirement savings.

If you convert $50,000 and pay the $12,000 tax from that same $50,000, you end up with only $38,000 in your Roth IRA. The $12,000 that went to taxes is gone and cannot grow tax-free. If you pay the tax from other savings instead, the full $50,000 stays in the Roth and grows tax-free forever. This is why financial advisors often recommend paying the tax from outside money if you can afford it — it maximizes the benefit of the conversion.

Some people do not have outside money and must pay the tax from the conversion itself. That is still a valid strategy; it just means less money ends up in the Roth account.

What happens if you miss the tax deadline

If you do not pay the tax by April 15, the IRS charges interest on the unpaid amount starting May 1. The interest rate changes quarterly and is currently around 8% per year, though it varies. You also owe a failure-to-pay penalty of 0.5% per month (up to 25% total) on the unpaid tax.

If you filed an extension and your deadline is October 15, the same rules apply — interest and penalties start accruing if you do not pay by then. Filing an extension gives you more time to file your return, but it does not extend the payment deadline unless you request a payment extension separately (which the IRS may grant if you have a good reason).

If you realize you cannot pay by the deadline, contact the IRS before it passes. You can request a short-term extension (up to 120 days) or set up a payment plan. Acting before the deadline is much simpler than dealing with penalties and interest after.

State income tax on conversions

Most states that have income tax treat Roth conversions the same way the federal government does: you owe state income tax on the converted amount in the year you convert. A few states do not tax retirement income at all (like Florida, Texas, and South Dakota), so residents of those states owe only federal tax. A handful of other states have special rules for retirees or certain types of retirement accounts.

Check your state's tax website or ask a tax professional if you live in a state with income tax. The state tax bill can be substantial — in California or New York, it could be 10% or more of the conversion amount on top of federal tax.

Timing conversions to reduce your tax bill

Because your tax bill depends on your total income that year, some people convert in years when their income is unusually low. A person who retires mid-year, takes a sabbatical, or experiences a job loss may have a year with much lower income than usual. Converting in that year means the conversion is taxed at a lower rate than it would be in a normal year.

This strategy requires planning. You need to know roughly what your income will be for the year before you convert, and you need to have time to execute the conversion before December 31. It also only works if you have flexibility about when you convert — if you need the money in the Roth immediately, timing may not be an option.

Frequently Asked Questions

Can I convert and not pay taxes on it?

No. The IRS requires you to pay income tax on the full amount you convert in the year you convert it. There is no way around this. The benefit of a Roth conversion is that the money grows tax-free after that point, not that the conversion itself is tax-free.

Do I owe taxes when I withdraw money from the Roth later?

No. Once you have paid tax on the conversion and the money sits in the Roth for at least five years, you can withdraw it tax-free at any age. You already paid the tax upfront, so the IRS does not tax you again.

What if I convert in December — do I owe taxes that year or next year?

You owe taxes in the year you convert, regardless of the month. A December conversion is reported on your tax return for that year (filed the following April), and the tax is due by April 15 of the following year. The conversion date is what matters, not the payment date.

Can I undo a conversion if the tax bill is too high?

You can reverse a conversion through a process called a recharacterization, but the rules are strict. You must do it by October 15 of the year after the conversion (or October 15 of the following year if you filed an extension). If you recharacterize, the conversion is treated as if it never happened, and you do not owe tax on it. However, you cannot recharacterize conversions made after 2017 in most situations — the rules changed significantly.

What if I cannot afford to pay the tax?

Contact the IRS before the deadline and request a payment plan. The IRS will set up an installment agreement where you pay the tax over time (usually 24 to 120 months). You will owe interest and a setup fee, but you avoid the failure-to-pay penalty if you stay current on the plan. Alternatively, do not convert the full amount — convert less so the tax bill is manageable.