The Backdoor Roth IRA

How it works

A Roth IRA has one access rule that a traditional IRA does not. IRC 408A(c)(3) bars a direct contribution once modified adjusted gross income clears a set threshold, with no exception for someone who simply wants to fund one anyway. The route around that limit runs in two separate steps, each governed by its own rule, and neither of those rules cares about income at all.

The first step is a contribution to a traditional IRA. There is no income limit on making one, at any income level. Once a taxpayer is above the deduction phase-out that applies to an active participant in a workplace retirement plan under IRC 219(g), that contribution is not deductible anyway, which is what creates basis in the account. The designated nondeductible contribution rule of IRC 408(o) is what makes that basis real, and it gets reported on Form 8606, Part I, for the year it is made.

The second step is a conversion of that traditional IRA to a Roth IRA. There is no income limit on a conversion either, and that was not always true: the income ceiling that used to apply to conversions was repealed for tax years after 2009. Because the contribution created basis rather than a deduction, IRC 408A(d)(3) does not tax that basis a second time when it converts. Whatever growth happened between the contribution and the conversion is ordinary taxable income on the way through, and no statutory waiting period separates the two steps, so that growth is usually small when the conversion follows promptly.

The result, when the surrounding accounts cooperate, is permanent. A qualified distribution from a Roth IRA is entirely tax-free, the account carries no lifetime required minimum distribution for the owner, and none of it would have been reachable through a direct contribution at this income level.

What this is worth in Florida

Less than the mechanism suggests, and it is worth saying plainly. Florida has no individual income tax, so a state tax bill on the conversion's taxable sliver was never in the picture for a Florida resident regardless of how this is done. Every part of what this is worth, the amount that avoids tax now and the growth that stays tax-free later, is a federal benefit end to end. There is no separate Florida angle to model and no state-level reason to prefer this over any other retirement account.

Who this applies to

This exists for one specific taxpayer: someone whose modified adjusted gross income sits above the point where a direct Roth contribution is allowed at all. Below that line, a direct contribution already works, Form 8606 never enters the picture, and none of this is worth the extra filing.

The 2026 phase-out for a direct Roth contribution runs from $153,000 to $168,000 of MAGI for a single filer or head of household, from $242,000 to $252,000 for a married couple filing jointly, and effectively from $0 to $10,000 for a married person filing separately. Those ranges move with inflation every year under IRC 408A(c)(3); the 2025 ranges were $150,000 to $165,000 single and $236,000 to $246,000 joint.

Above the top of that range, IRC 408A(c)(3) blocks a direct Roth contribution outright, at any income level. It does not block a nondeductible traditional IRA contribution, and it does not block a Roth conversion; neither of those two steps carries an income ceiling of its own. That asymmetry is the entire premise, and it only exists because Congress removed the income cap that used to apply to conversions, effective for tax years after 2009. Before that repeal, the conversion step carried an income ceiling of its own.

This is also a different question from a lump-sum Roth conversion of an existing pretax balance, which someone with no income-limit problem at all might still have reasons to consider. Here, the income limit on a direct contribution is the only reason the two-step version exists in the first place.

What it requires

The two steps themselves are simple. What actually gates a clean result is a short list of conditions, and the last one is the condition taxpayers miss most often.

• Earned compensation for the year, at least equal to whatever is contributed. IRC 219(f)(1) sets this requirement for any IRA contribution, and it applies here exactly as it does anywhere else.
• A contribution within the annual limit, indexed for inflation each year. In 2026 the base limit is $7,500, with an additional $1,100 available at age 50 and older, for a combined $8,600; the 2025 limit was $7,000, or $8,000 with the catch-up under IRC 219(b)(5)(B), which is the IRA catch-up and a different provision from the IRC 414(v) catch-up that applies to employer plans. A spouse with no compensation of their own can use the same limit on a joint return under IRC 219(c).
• The contribution and the paperwork made on time. A given year's contribution can be made as late as the unextended return due date the following April under IRC 219(f)(3), and Form 8606 for both steps is due with the 1040, including any extension.
• No balance in any traditional, SEP, or SIMPLE IRA on December 31 of the conversion year. This is the condition that decides whether the result comes out close to tax-free or mostly taxable. IRC 408(d)(2) treats every traditional, SEP, and SIMPLE IRA a taxpayer owns as one contract for this purpose, no matter how many accounts or custodians are involved. A Roth IRA sits outside that pool, and so does a 401(k) or 403(b) balance at an employer plan. A taxpayer who has other pretax IRA money and wants a clean conversion has one option: move it into an employer plan that accepts incoming rollovers before the December 31 measuring date. My solo 401(k) vs. SEP-IRA guide covers the kind of plan that can receive it.

No statutory waiting period separates the contribution from the conversion. That timing flexibility is not itself the benefit; the pool being clean when December 31 arrives is what actually decides how this comes out.

What you need to document

None of this is complicated on its own, but it depends on a paper trail that has to hold up for as many years as there is unrecovered basis sitting on record, which can be a long time.

Form 8606, Part I, for every year with a nondeductible contribution

Line 1 reports the current year's nondeductible amount, line 2 carries forward prior basis, and line 6 reports the year-end value of every traditional, SEP, and SIMPLE IRA in existence. That last figure is what the pro-rata fraction gets built from, and it has to reflect the December 31 balance, not the balance on any other date.

Form 8606, Part II, for every year with a conversion

Line 16 is the amount converted, line 17 is the basis allocated to it, and line 18 is the taxable result that carries to Form 1040. A zero on line 18 is only correct if Part I and the year-end balance reported on line 6 actually support it.

A basis ledger that survives from one year to the next

Line 14 carries unrecovered basis forward. A missing year breaks that chain, and the practical result is not just a gap in the paperwork. It is the IRS treating a later distribution as fully taxable because the basis was never on record, which taxes the same dollars a second time.

A year-end statement for every traditional, SEP, and SIMPLE IRA that exists

Including accounts nobody thinks of as relevant to this year's activity, such as an old SEP-IRA from earlier years of self-employment or a rollover IRA from a job left a decade ago. Any of them counts toward the pool on December 31, whether or not it was touched this year.

Where it goes wrong

This is not a position the IRS treats as abusive. It is not a listed or reportable transaction, and converting a nondeductible contribution shortly after making it has not drawn a step-transaction challenge when it was reported correctly. What actually causes trouble is arithmetic and paperwork, not the structure of the maneuver itself.

The pro-rata rule is the one that matters

IRC 408(d)(2) treats every traditional, SEP, and SIMPLE IRA a taxpayer owns as a single contract, and treats every distribution from any of them, including a conversion, as coming proportionally from basis and pretax money together rather than from whichever account the money physically sat in. A nondeductible contribution sitting next to a much larger pretax balance from an old rollover or an employer SEP-IRA does not convert cleanly; most of it converts as ordinary taxable income, in direct proportion to how small the basis is against the combined total. That fraction is measured against the December 31 balance across every account the taxpayer owns, not just the one that received this year's contribution, and not the balance on the day of the conversion. A taxpayer who runs a SEP-IRA for themselves and also wants a clean backdoor Roth has to solve for both accounts at the same time, because the SEP-IRA sits in exactly the same pool.

The other ways this goes sideways

• Form 8606 never gets filed. IRC 6693(b)(2) sets a $50 penalty for each year a required Form 8606 goes unfiled, absent reasonable cause. The larger cost shows up later: unreported basis means there is no record that any of this was ever taxed, and a future distribution gets taxed again in full.
• The contribution exceeds what earned compensation or the annual limit allows. IRC 4973 imposes a 6 percent excise tax on the excess for every year it stays uncorrected. Converting an excess contribution to Roth does not fix the excess; the excise tax keeps running until it is actually corrected.
• The taxpayer never needed any of this. Someone whose income already sits under the Roth phase-out gets nothing from the two-step version that a direct contribution would not already give, at the cost of an extra Form 8606 filing in every year there is activity.

Since 2018, IRC 408A(d)(6)(B)(iii) bars recharacterizing a Roth conversion. A conversion made while the IRA pool was not actually clean cannot be undone once it happens. Whatever the pro-rata fraction turns out to be, it is permanent.

A situation where this comes up

The clean version of this is a self-employed taxpayer running an S corporation, well past the joint filing phase-out, whose entity retirement plan is a solo 401(k) rather than a SEP-IRA. Because a 401(k) balance sits outside the pro-rata pool entirely, a nondeductible contribution and a same-week conversion come through close to tax-free, and the only real work left is remembering to file both parts of Form 8606 on time, every year there is activity.

The harder version is the same taxpayer with an old SEP-IRA still open from earlier years of self-employment, or a rollover IRA left over from a job before this one. Both sit in the pro-rata pool on December 31 whether or not either one is touched this year. A clean conversion means moving that balance into a plan that accepts incoming rollovers, such as a solo 401(k), before year-end; my guide to choosing between a solo 401(k) and a SEP-IRA covers what that receiving plan needs to look like for someone in this position. Skipping that step does not block the contribution or the conversion. It just means most of what converts is taxable, with no way to undo it afterward.

The version that concerns me is the taxpayer who converts first and checks the account list after. By the time the pro-rata fraction shows up on Form 8606, the conversion has already happened, the tax has already been incurred, and IRC 408A(d)(6)(B)(iii) leaves no recharacterization available to fix it. The order matters here more than almost anywhere else in the tax code, because this is one of the few positions where getting the sequence backward is not just costly. It is unfixable.