If you read enough FI blogs, you will eventually come across the term “Backdoor Roth IRA.” This post answers the question “What’s the deal with Backdoor Roth IRAs?”

Why Do a Backdoor Roth IRA?

Why would someone do a Backdoor Roth IRA? The Backdoor Roth IRA gets money into a Roth IRA in cases where the taxpayer earns too much to make a direct annual contribution to a Roth IRA. Doing the Backdoor Roth IRA gets money that would have been invested in a taxable account into a tax-free Roth account. Further, the money in the Roth account gets better creditor protection than money in a taxable account.

History of the Backdoor Roth IRA

Before 2010, what is now referred to as a Backdoor Roth IRA would have been permissible and/or necessary in only relatively limited circumstances, and then only in years prior to 2008. But a 2006 change in the law opened up the Backdoor Roth IRA in the form we know now (starting in 2010).

Two fundamental concepts must now be addressed. The first is a Roth IRA contribution.

Roth IRA Contributions

This post discusses Roth IRA contributions in detail. Simplified, U.S. citizens and residents with earned income can make an annual Roth IRA contribution of up to $7,000 in 2024 ($8,000 if 50 or older). Done for many years, it can be a tremendous wealth building tool, since it moves wealth into an account that is tax-free (if properly executed).

The one catch is that your “modified adjusted gross income” (or “MAGI”) must be below a certain threshold in order to make a Roth IRA contribution. To make a full contribution in 2024, your MAGI must be less than $146,000 (if single) or $230,000 (if married filing joint).

Because of these limits, many taxpayers are unable to make a Roth IRA contribution. Further, based on the qualification rules for traditional deductible IRA contributions, most taxpayers unable to make a Roth IRA contribution are also unable to make a deductible traditional IRA contribution.

Roth IRA Conversions

The second fundamental concept is a Roth IRA conversion. A Roth IRA conversion is a movement of amounts in traditional accounts to a Roth IRA. This creates a taxable event. The amount of the Roth IRA conversion, less any “basis” in the traditional account (more on that later), is taxable as ordinary income on the taxpayer’s tax return.

Prior to 2010, only taxpayers with a modified adjusted gross income of $100,000 or less were allowed to do a Roth IRA conversion. This amount was not indexed for inflation and applied per tax return, making it particularly difficult for many married couples to qualify.

In 2006, Congress changed the law, effective beginning in 2010. As of January 1, 2010, there is no modified adjusted gross income limitation on the ability to do a Roth IRA conversion. The richest, highest earning Americans now qualify to do a Roth IRA conversion just as easily as anyone else.

The Backdoor

Okay, so there’s no MAGI limitation on the ability to execute a Roth IRA conversion. So what? Aren’t they taxable? What’s the advantage of doing one?

Recall I mentioned a taxpayer’s basis in a traditional account. Basis in an IRA occurs when a taxpayer makes a nondeductible contribution to a traditional IRA. Here is an example.

Mike expects to earn $300,000 from his W-2 job in 2024, is covered by a workplace 401(k) plan, and expects to have some investment income. Mike has no balance in a traditional IRA, SEP IRA, or SIMPLE IRA.

Mike contributes $7,000 to a traditional IRA on April 20, 2024. The contribution is nondeductible. Because the contribution is nondeductible, Mike gets a $7,000 basis in his traditional IRA. Mike must file a Form 8606 with his 2024 tax return to report the nondeductible contribution.

The “backdoor” opens because of the confluence of two rules: the ability to make a nondeductible traditional IRA contribution and the ability to do a Roth IRA conversion regardless of your income level. Let’s extend Mike’s example a bit.

On May 2, 2024, Mike converts all the money in his traditional IRA to a Roth IRA (a Roth IRA conversion). At that time, Mike’s traditional IRA had a value of $7,011.47.

What result? To start, all $7,011.47 is taxable. All money converted in a Roth IRA conversion is taxable. Uh oh! But there’s good news for Mike. Mike gets to offset the $7,011.47 that is taxable by the $7,000 of basis in his traditional IRA. Thus, this Roth IRA conversion will only increase Mike’s taxable income by $11.47 ($7,011.47 minus $7,000).

The combination of these two separate, independent steps (a nondeductible traditional IRA contribution and a later Roth IRA conversion) is what many now refer to as the Backdoor Roth IRA. Notice this is only possible because of the repeal of the MAGI limitation on Roth IRA conversions. Under the rules effective prior to 2010, Mike would have been allowed to make the nondeductible traditional IRA contribution, but his income (north of $300,000) would have prohibited him from a Roth IRA conversion.

The Backdoor Roth IRA allows Mike to obtain the benefits of an annual Roth IRA contribution without qualifying to make a regular annual Roth IRA contribution.

December 31st

Any Backdoor Roth IRA planning should involve an additional diligence step: ensuring that as of December 31st of the year of the Roth conversion step, the taxpayer has a zero balance in all traditional IRAs, SEP IRAs, and SIMPLE IRAs. This helps ensure the Backdoor Roth IRA is a tax-efficient tactic.

The Pro-Rata Rule

The Backdoor Roth IRA works well for someone with Mike’s profile. But it does not work well for everyone. Let’s change up the example a bit.

Jennifer’s story is the same as Mike’s story above, except that she had a separate traditional IRA before she did her 2024 nondeductible IRA contribution. That separate IRA had no basis. As of December 31, 2024, that separate traditional IRA was worth $92,988.53.

This one change in facts dramatically increases Jennifer’s taxable income from the Roth IRA conversion. Jennifer must apply the so-called Pro-Rata Rule to the Roth IRA conversion. Even though her two IRAs are in separate accounts, they are treated as one IRA for purposes of determining how much of Jennifer’s $7,000 of basis she recovers upon her Roth IRA conversion.

Jennifer starts with $7,011.47 of income (the amount she converts). To determine the amount of her $7,000 of basis she gets to recover against the proceeds of the Roth IRA conversion, we must multiply that $7,000 times the amount converted ($7,011.47) divided by the sum of the amount converted and her traditional IRA balance at the end of the year ($7,011.47 plus $92,988.53). Thus, Jennifer gets to recover 7.00147 percent of the $7,000 of basis, which is only $490.80. This results in Jennifer’s Roth IRA conversion increasing her taxable income by $6,520.67 ($7,011.47 minus $490.80).

What was a great idea for Mike becomes a horrible idea for Jennifer when she has a significant balance in another traditional IRA.

Note further that Jennifer would have the same bad outcome if that $92,988.53 traditional IRA was instead in a traditional SEP IRA or in a traditional SIMPLE IRA.

Tax Reporting

Assume Mike did his Roth IRA conversion and did not have any other money in traditional IRAs in 2024. He will get a Form 1099-R from his financial institution. In box 1 it will report a gross distribution of $7,011.47 (the amount of the Roth IRA conversion).

In box 2a the Form 1099-R will say that the “taxable amount” is $7,011.47 and box 2b will be checked to indicate that the “taxable amount not determined.” Wait, what? How can $7,011.47 be the taxable amount while the next box claims the taxable amount is not determined? The answer is the basis concept discussed above.

Mike’s financial institution does not know the rest of Mike’s story (his income, retirement plan coverage at work, IRAs at other institutions, etc.), so it has no way of determining how much basis, if any, Mike recovers when he did the Roth IRA conversion. Box 2b simply means that Mike might have recovered some basis, but the institution is not in a position to determine if he did.

Form 8606 helps complete the tax reporting picture. By filing that form, Mike establishes that he was entitled to $6,000 of traditional IRA basis and how the pro-rata rule applies (if at all) to his Roth IRA conversion. It is important that Mike file a properly completed Form 8606 with his timely-filed 2024 federal income tax return.

When Mike files his 2024 Form 1040, he puts $7,011.47 on line 4a (“IRA distributions”) and $11.47 on line 4b (“Taxable amount”). Most tax return preparation software will round cents to the nearest whole dollar.

Note that failing to report the transactions on the Forms 8606 and 1040 in this way can result in Mike paying an incorrect amount of tax.

Further Reading

This post discusses what you can do if you find yourself in Jennifer’s situation to get a result similar to Mike’s result. I discuss how to properly report a Backdoor Roth IRA on your tax return and what to do if has been incorrectly reported here.

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This post is for entertainment and educational purposes only. It does not constitute accounting, financial, investment, legal, or tax advice. Please consult with your advisor(s) regarding your personal accounting, financial, investment, legal, and tax matters. Please also refer to the Disclaimer & Warning section found here.