Backdoor Roth IRA explained: how high earners get into a Roth legally

The Roth IRA is one of the best deals in the U.S. tax code: you contribute money you have already paid tax on, it grows tax-free, and qualified withdrawals in retirement are completely untaxed. The catch is an income ceiling. Once your modified adjusted gross income (MAGI) climbs past a certain point, you are no longer allowed to contribute directly. For 2024 that phase-out started at $146,000 for single filers and $230,000 for married couples filing jointly — and those numbers move up a little each year.

That is where the backdoor Roth IRA comes in. It is not a loophole in the shady sense; it is two ordinary, fully legal rules used back to back. Anyone — regardless of income — can put money into a traditional IRA without taking the deduction, and anyone can convert a traditional IRA to a Roth with no income limit. Chain those two together and a high earner who is "too rich" for a Roth can still get money into one.

Why the Roth is worth the trouble

Before the mechanics, the motivation. Money inside a Roth grows and is withdrawn tax-free, there are no required minimum distributions during your lifetime, and your heirs inherit it tax-free too. For someone who expects to be in a similar or higher tax bracket later — or who simply wants tax diversification — that is powerful. If you are still deciding whether the Roth wrapper is right for you at all, our guide on whether a Roth IRA is worth it walks through the trade-offs first.

The two steps, in order

At its core the backdoor Roth is genuinely simple. The complexity is all in the details that follow.

• Step 1 — Contribute. Put money into a traditional IRA as a non-deductible contribution. Because your income is high you cannot deduct it anyway, so you are funding it with after-tax dollars.
• Step 2 — Convert. Move that money from the traditional IRA into a Roth IRA via a Roth conversion. Since the contribution was already after-tax, very little or no tax is due on the conversion — if you have no other pre-tax IRA money (more on that below).

Done cleanly, the result is the same as if you had simply contributed directly to a Roth: the annual contribution limit applies ($7,000 in 2024, or $8,000 if you are 50 or older), and the money now grows tax-free forever.

The step-by-step playbook

Here is the sequence most people follow, with the watch-outs at each stage.

Step	Action	Watch out for
1	Open (or use) a traditional IRA at your brokerage	It must be a traditional IRA, not a Roth or SEP
2	Make a non-deductible contribution (up to the annual limit)	Do not claim a deduction on your tax return
3	Leave it in cash; wait until it settles	Any gains before converting are taxable
4	Convert the full balance to your Roth IRA	The pro-rata rule if you hold other pre-tax IRAs
5	Invest the money inside the Roth	It does nothing sitting in cash
6	File Form 8606 for the year	Skipping it can mean paying tax twice

A practical note on timing: many people convert within days of contributing so there are almost no earnings to tax. Converting a small gain is fine and only adds a tiny tax bill, so do not panic if a few dollars of interest appear before you convert.

The pro-rata rule: the trap that catches everyone

This is the single most important paragraph on the page. The IRS does not let you cherry-pick which dollars you convert. Under the pro-rata rule, it treats all of your traditional, SEP and SIMPLE IRAs as one combined pool on December 31 of the conversion year. The taxable portion of any conversion is the ratio of pre-tax money to your total IRA balance.

If your only IRA money is the fresh non-deductible contribution, the ratio is clean: almost nothing is taxable. But if you already hold a large pre-tax traditional IRA — say from an old 401(k) rollover — that balance "contaminates" the conversion and makes most of it taxable.

Situation	Pre-tax IRA	New after-tax	Convert	Taxable share
Clean backdoor	$0	$7,000	$7,000	~0%
Has old rollover	$93,000	$7,000	$7,000	93%

In the second row, $93,000 of pre-tax money sits alongside $7,000 of after-tax money, so 93% of every dollar you convert is taxable — roughly $6,510 of that $7,000 conversion gets taxed at your ordinary rate. That defeats most of the benefit. The common fix is to "roll the pre-tax IRA away" first: if your employer's 401(k) accepts incoming rollovers, move the pre-tax IRA into the 401(k) before December 31. That empties the IRA pool and leaves only the after-tax dollars to convert. This is exactly the kind of move worth running past a CPA before you pull the trigger.

Form 8606: the paperwork you cannot skip

Because the money went in as after-tax dollars, you need to tell the IRS so you are not taxed on it a second time when you convert. That is the job of Form 8606. Part I reports your non-deductible contribution and establishes your basis — the after-tax money the IRS should never tax again. Part II reports the conversion itself.

File Form 8606 for the year you make the contribution and again for the year you convert (often the same return). If you forget it, your brokerage and the IRS may assume the whole conversion is taxable, and you could end up paying tax on money you already paid tax on. Keep copies — the basis carries forward year after year, so good records matter.

The mega backdoor Roth, briefly

The standard backdoor moves at most a few thousand dollars a year. The mega backdoor Roth can move tens of thousands — but it lives inside your 401(k), not an IRA. It works like this:

• You make after-tax (non-Roth) contributions to your 401(k), above and beyond the normal pre-tax/Roth limit, up to the overall plan maximum ($69,000 in 2024 including employer match).
• You then convert those after-tax dollars to Roth — either through an in-plan Roth conversion or by rolling them out to a Roth IRA via an in-service withdrawal.

The catch is that your specific plan must allow both after-tax contributions and a way to convert them. Many plans do not. Check your summary plan description or ask your benefits team. If your plan qualifies, it is one of the most powerful tax-free savings moves available to a high earner. Either way, it is worth understanding how your 401(k) and a Roth IRA fit together — see our breakdown of 401(k) vs Roth IRA.

Who should — and should not — bother

The backdoor Roth is built for people above the Roth income limit who have maxed out other tax-advantaged space and want more tax-free growth. It is a poor fit if you hold large pre-tax IRA balances you cannot easily roll into a 401(k), because the pro-rata rule will tax most of the conversion. It is also unnecessary if your income is still below the Roth limit — in that case just contribute to the Roth directly and skip the paperwork. To see how much your retirement accounts could grow either way, the retirement and 401(k) calculator projects the long-run balance.

Common mistakes that cost money

• Ignoring the pro-rata rule and triggering a surprise tax bill on a conversion you thought was tax-free.
• Forgetting Form 8606, which can lead to being taxed twice on the same dollars.
• Leaving the money in cash inside the Roth and forgetting to invest it.
• Contributing for the wrong year — contributions can be made up to the tax-filing deadline, so be clear which year you are funding.
• Assuming your 401(k) supports the mega version without checking the plan rules first.

Frequently asked questions