The basic mechanics of a backdoor Roth

A backdoor Roth IRA is a two-step process: you put after-tax money into a traditional IRA, then move that money into a Roth IRA. The IRS allows this conversion because you are moving money you have already paid income tax on, so the Roth account receives funds that have been taxed once.

The reason people use this method is income limits. The IRS sets income thresholds above which you cannot contribute directly to a Roth IRA. A backdoor Roth bypasses that rule because there is no income limit on converting a traditional IRA to a Roth IRA — only on direct contributions. For 2024, if your Modified Adjusted Gross Income (MAGI) exceeds $161,000 (single) or $240,000 (married filing jointly), you cannot make a direct Roth contribution, but you can still do a backdoor conversion.

The conversion itself is not automatic. You must file Form 8606 with your tax return in the year you convert. This form tells the IRS you are moving pre-tax and after-tax money between accounts and calculates how much of the conversion is taxable.

Key Takeaways

  • A backdoor Roth involves depositing after-tax money into a traditional IRA, then converting that IRA to a Roth IRA within the same tax year.
  • You must file Form 8606 with your tax return to report the conversion; without it, the IRS may treat the transaction as a taxable distribution.
  • If you have other traditional IRAs with pre-tax balances, the pro-rata rule requires you to pay income tax on a portion of the conversion based on your total IRA balance.
  • The conversion itself is not a taxable event if you convert only after-tax contributions, but any earnings on that money are taxable in the year of conversion.
  • You can do a backdoor Roth in any year, regardless of income, as long as you have earned income to support the contribution amount.

Step one: contribute after-tax money to a traditional IRA

Open or use an existing traditional IRA at a bank, brokerage, or investment firm. Deposit money you have already paid income tax on — this is not a tax-deductible contribution. The amount you can deposit is the same as a regular IRA contribution limit: $7,000 for 2024 if you are under 50, or $8,000 if you are 50 or older.

You do not have to wait any length of time between the deposit and the conversion. Many people deposit and convert in the same week or even the same day. The key is that both the contribution and the conversion happen in the same tax year so they appear on the same Form 8606.

Keep records of this deposit. You will need to show the IRS that this money was after-tax (non-deductible). Your brokerage will send you a Form 5498 in January showing the contribution amount, but you should also keep your own bank or wire transfer records as backup.

Step two: convert the traditional IRA to a Roth IRA

Once the money is in the traditional IRA, instruct your financial institution to convert it to a Roth IRA. Most brokerages have a straightforward online form or phone process for this. You can convert the entire balance or only part of it — the choice is yours.

The conversion generates a Form 1099-R from your financial institution, which reports the amount converted. This form will show up on your tax return and is what triggers the need to file Form 8606.

The timing matters for tax purposes. If you convert in 2024, you report it on your 2024 tax return filed in 2025. The IRS does not care when in the year you convert — January or December makes no difference — only that the contribution and conversion both happen within the same calendar year.

The pro-rata rule and why other IRAs matter

If you have any other traditional IRAs, SEP IRAs, or straightforward IRAs with pre-tax money in them, the pro-rata rule applies. This rule says the IRS treats all your IRAs as one pool for tax purposes. When you convert, you cannot cherry-pick only the after-tax money — you must convert a proportional mix of pre-tax and after-tax funds.

Here is how it works: suppose you have $50,000 in a traditional IRA (pre-tax) and you contribute $7,000 after-tax to another traditional IRA, then convert that $7,000. The IRS sees your total IRA balance as $57,000, of which $50,000 is pre-tax. That means 87.7% of your conversion is pre-tax money. You owe income tax on $6,140 of the $7,000 converted, even though you only converted the after-tax portion.

This is the most common reason a backdoor Roth fails or creates an unexpected tax bill. If you have a rollover IRA from an old 401(k), a SEP IRA from self-employment, or any other pre-tax IRA balance, you must account for it before converting. Some people solve this by rolling their pre-tax IRA into their current employer's 401(k) plan (if the plan allows it), which removes it from the pro-rata calculation.

Tax consequences of the conversion

If you convert only after-tax contributions with no earnings, you owe no income tax on the conversion itself. The money goes into the Roth tax-free because you already paid tax on it once.

If the after-tax money has earned interest, dividends, or investment gains while sitting in the traditional IRA, that earnings portion is taxable in the year of conversion. For example, if you deposit $7,000 after-tax and it grows to $7,300 before you convert, you owe income tax on the $300 gain. This tax is due when you file your return for that year.

The pro-rata rule also creates a tax bill. If the rule applies and part of your conversion is pre-tax money, you owe income tax on that portion at your ordinary income tax rate for the year.

Once the money is in the Roth IRA, all future growth is tax-free, and you can withdraw it tax-free after age 59½ (with some exceptions for withdrawals within five years of the conversion).

Filing Form 8606 and reporting to the IRS

Form 8606 is the document that tells the IRS you did a backdoor Roth conversion. You must file it with your tax return in the year of the conversion. If you do not file it, the IRS may treat the entire conversion as a taxable distribution, which can result in a much larger tax bill and potential penalties.

The form asks for the amount of your IRA contributions (both deductible and non-deductible), the value of all your IRAs on December 31 of that year, and the amount you converted. It then calculates how much of the conversion is taxable based on the pro-rata rule.

You file Form 8606 even if you owe no tax on the conversion. This creates a record with the IRS showing that the conversion was intentional and that you reported it correctly. Without this filing, the IRS has no way to know you did a backdoor Roth rather than a taxable withdrawal.

Common mistakes and how to avoid them

The most frequent error is forgetting about the pro-rata rule. People assume that because they contributed after-tax money, the entire conversion is tax-free. If you have any pre-tax IRA balance, this assumption is wrong. Before you do a backdoor Roth, add up all your traditional, SEP, and straightforward IRA balances and calculate the pro-rata percentage.

Another mistake is converting in one year but reporting it in another. The contribution and conversion must both happen in the same calendar year. If you contribute in December 2024 but do not convert until January 2025, the IRS treats them as separate events in separate years, which can create tax complications. Always convert within the same year you contribute.

Some people also fail to keep records of the after-tax contribution. Your brokerage will report the contribution on Form 5498, but you should also keep your own documentation — bank statements, wire confirmations, or deposit receipts — to prove the money was after-tax if the IRS ever questions it.

Finally, not filing Form 8606 is a critical error. Even if you owe no tax, you must file the form. The penalty for not filing can be substantial, and it can take years to correct the record with the IRS.

Frequently Asked Questions

Can I do a backdoor Roth if I have a 401(k) at work?

Yes. The pro-rata rule applies only to IRAs (traditional, SEP, and straightforward), not to 401(k)s, 403(b)s, or other employer plans. If all your pre-tax money is in a 401(k), you can do a backdoor Roth without triggering the pro-rata rule. However, if you have both a 401(k) and a traditional IRA with pre-tax money, the rule still applies to the IRA portion.

What happens if I convert and then the market drops before I file my taxes?

You can file Form 8606 showing the value on the conversion date, not the value when you file your return. However, if the value drops significantly, you may be able to recharacterize the conversion (move the money back to a traditional IRA) and redo it later. Recharacterization rules are strict and have important date, so consult a tax professional if this situation applies to you.

Do I have to convert the entire after-tax IRA balance, or can I convert only part of it?

You can convert any amount you choose. You do not have to convert the entire balance. However, the pro-rata rule still applies to whatever you convert. If you convert $3,500 of a $7,000 after-tax contribution, the pro-rata calculation still includes your full IRA balance.

Can I do a backdoor Roth if I have no earned income?

No. To make any IRA contribution (traditional or Roth, direct or backdoor), you must have earned income at least equal to the amount you contribute. Earned income means wages, self-employment income, or other compensation from work. Investment income, retirement distributions, or spousal income do not count unless you file taxes as married filing jointly and your spouse has earned income.

How long do I have to wait after converting before I can withdraw the money?

You can withdraw the after-tax contributions you converted at any time without penalty. However, if you withdraw the earnings on that money or any pre-tax portion of the conversion within five years of the conversion, you may owe a 10% penalty plus income tax. After five years and age 59½, all withdrawals are tax-free.