How a Backdoor Roth IRA Conversion Actually Works

By Felix Thorpe · Retirement Accounts WriterPublished October 8, 2026

The Basic Mechanics of a Backdoor Roth

A backdoor Roth IRA works in two steps: you contribute money to a traditional IRA (which has no income limit), then convert that money to a Roth IRA (which does have an income limit for direct contributions). The IRS allows anyone to convert a traditional IRA to a Roth IRA regardless of income, which is why this route exists for people who earn too much to contribute directly to a Roth.

The conversion itself is straightforward mechanically. You instruct your IRA custodian (your bank, brokerage, or investment firm) to move the money from the traditional IRA to a Roth IRA. You then report the conversion on your tax return using Form 8606. The custodian will send you a 1099-R form showing the amount converted, and you use that to fill out Form 8606.

The timing between the contribution and the conversion does not matter legally—you can do both on the same day, or wait weeks or months. Many people do them on the same day to minimize the risk of market movement or the pro-rata rule complications (explained below).

Key Takeaways

A backdoor Roth lets you move money into a Roth IRA even if your income is too high for a direct Roth contribution.
You contribute to a traditional IRA first, then convert that money to a Roth IRA, and report it on Form 8606 when you file taxes.
If you already have money in a traditional IRA, SEP IRA, or SIMPLE IRA, the pro-rata rule may force you to pay tax on part of the conversion.
The conversion itself is taxable income in the year you do it, but only on the portion that was not already taxed.
Backdoor Roths work the same way every year—there is no limit to how many times you can do one.

Why the Pro-Rata Rule Changes the Tax Bill

The pro-rata rule is the part of a backdoor Roth that catches most people off guard. If you have any money sitting in a traditional IRA, SEP IRA, or SIMPLE IRA on December 31 of the year you convert, the IRS treats all your IRAs as one pool for tax purposes. You cannot convert only the new, non-deductible contribution and leave the old, pre-tax money behind.

Here is a concrete example: suppose you have a traditional IRA with $50,000 in pre-tax contributions (money you deducted when you contributed it). You then contribute $7,000 to a new traditional IRA and immediately convert it to a Roth. The IRS sees $57,000 total in traditional IRAs. Your $7,000 conversion is treated as 12% non-taxable ($7,000 ÷ $57,000) and 88% taxable ($50,000 ÷ $57,000). You owe income tax on $6,160 of the conversion.

The pro-rata rule applies to the calendar year, not to individual accounts. It does not matter if your $50,000 is in one IRA or five different IRAs—the IRS counts them all together. It also does not matter if the $50,000 is at a different custodian than the new $7,000.

The Tax You Owe on Conversion

When you convert a traditional IRA to a Roth, you owe federal income tax on the amount that was not already taxed. If you contributed $7,000 in after-tax dollars (non-deductible contribution) and converted it immediately with no pro-rata complications, you owe zero tax on that conversion. If the $7,000 was pre-tax money, or if the pro-rata rule applies, you owe tax at your ordinary income tax rate for that year.

The conversion is reported as income on your tax return. If you convert $7,000 and owe tax on $6,160 of it, that $6,160 is added to your other income for the year. If you are in the 24% federal tax bracket, you owe roughly $1,478 in federal tax on that conversion. State income tax may apply as well, depending on where you live.

You do not have to pay the tax out of the IRA itself. You can pay it from your regular bank account or paycheck. Many people do this because taking money out of the IRA to pay the tax would trigger another taxable event and defeat the purpose of the conversion.

Avoiding the Pro-Rata Rule Trap

The cleanest way to avoid the pro-rata rule is to have zero dollars in any traditional, SEP, or SIMPLE IRA on December 31 of the year you convert. If you have an old 401(k) or 403(b) from a previous job, those do not count toward the pro-rata rule—only IRAs do.

If you have an existing traditional IRA with pre-tax money, you have three options. First, you can roll the traditional IRA into your current employer's 401(k) plan (if the plan accepts rollovers). This removes it from the pro-rata calculation. Second, you can wait until you retire or leave your job and roll it into a new employer plan at that time. Third, you can convert the entire traditional IRA to a Roth in the same year as your backdoor contribution, paying tax on all of it at once.

The first option—rolling into a 401(k)—is the most common solution. Contact your employer's plan administrator or benefits department and ask whether the plan accepts "incoming rollovers" from IRAs. If it does, your IRA custodian can transfer the money directly to the 401(k). This move must happen before December 31 to clear the pro-rata rule for that year.

The Nondeductible Contribution Form You Must File

Even if you owe zero tax on your backdoor Roth, you must file Form 8606 with your tax return. This form tells the IRS that you made a nondeductible contribution to a traditional IRA and converted it. If you do not file Form 8606, the IRS may assume the entire conversion was taxable, and you could face a tax bill or an audit notice.

Form 8606 asks for the total value of all your IRAs on December 31, the amount you converted, and the taxable portion. If you converted $7,000 with no pro-rata complications, you report $7,000 as the conversion amount and $0 as the taxable portion. Your tax software usually walks you through this, but if you are filing by hand or working with a tax preparer, make sure they know you did a backdoor Roth.

Keep records of the nondeductible contribution. Your IRA custodian will send you a 1099-R form showing the conversion, but you should also keep your own records showing that the $7,000 was contributed in after-tax dollars. This protects you if the IRS ever questions the conversion.

Doing a Backdoor Roth Every Year

There is no rule against doing a backdoor Roth more than once. Many high-income earners do one every year to max out their Roth contributions. For 2024, the annual contribution limit for a traditional IRA is $7,000 (or $8,000 if you are 50 or older). You can contribute that amount to a traditional IRA and convert it to a Roth in the same year, then do it again the following year.

Each year is a separate tax event. If you do a backdoor Roth in January 2024 and another in January 2025, you file Form 8606 for each year on the respective tax returns. The pro-rata rule applies separately to each calendar year, so having a successful backdoor Roth in 2024 does not affect your 2025 conversion.

The main thing to track is the pro-rata rule each December 31. If you do a backdoor Roth in March and still have a traditional IRA balance in December, the pro-rata rule applies to that March conversion. Plan accordingly by rolling old IRAs into a 401(k) before the end of the year if you know you will be doing a backdoor Roth.

What Happens After the Money Is in the Roth

Once the money is in the Roth IRA, it grows tax-free. You do not owe tax on the earnings, and you do not have to take withdrawals at any age (unlike traditional IRAs, which require required minimum distributions starting at age 73). You can withdraw your contributions (the original $7,000) at any time without penalty. Earnings can be withdrawn tax-free after age 59½ if the Roth has been open for at least five years.

The five-year rule is per Roth IRA account, not per person. If you open a new Roth IRA to receive your backdoor conversion, that Roth's five-year clock starts on January 1 of the year you opened it. If you already have a Roth IRA from years past, the five-year clock started when you first opened any Roth IRA, and it has likely already passed.

Frequently Asked Questions

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

Yes. A 401(k) does not count toward the pro-rata rule—only traditional, SEP, and SIMPLE IRAs do. You can have a 401(k) and do a backdoor Roth without any tax complications from the 401(k).

What if I convert in December but do not file Form 8606 until April?

You must file Form 8606 with your tax return for the year you converted, even if you file late. The form is due when your return is due. If you miss the deadline, file an amended return (Form 1040-X) with Form 8606 as soon as you realize the mistake. The IRS may assess penalties if the form is filed very late.

Does a backdoor Roth count toward the $7,000 annual contribution limit?

Yes. The $7,000 limit applies to all contributions to traditional and Roth IRAs combined in a single year. If you contribute $7,000 to a traditional IRA and convert it, you have used your full $7,000 limit for that year and cannot make another IRA contribution.

What if the market drops between my contribution and conversion?

You still owe tax on the full amount you converted, not the current value. If you contribute $7,000 and it drops to $6,500 before you convert, you convert $6,500 but still owe tax based on the original contribution amount (assuming no pro-rata rule). The loss is locked in, but you do not get a tax deduction for it.

Can I do a backdoor Roth if I am self-employed?

Yes, but be careful with the pro-rata rule if you have a SEP IRA or Solo 401(k). A SEP IRA counts toward the pro-rata rule, so you may need to roll it into a Solo 401(k) first. A Solo 401(k) does not count toward the pro-rata rule, so you can do a backdoor Roth without complications if your only retirement account is a Solo 401(k).