Backdoor Roth IRA Example: Steps, Pro-Rata, and Form 8606

A backdoor Roth IRA example looks like this: a 40-year-old single filer earning $200,000 contributes $7,500 to a brand-new Traditional IRA on Monday, waits two days for the money to settle, and on Wednesday converts the full balance to a Roth IRA. Because the contribution was non-deductible and no other pre-tax IRA money exists, the $7,500 moves into the Roth tax-free. Only the tiny sliver of settlement-fund interest earned in those two days, maybe a dollar, counts as taxable income. That is the entire maneuver when it goes cleanly.

The strategy exists because direct Roth IRA contributions phase out at higher incomes, but non-deductible Traditional IRA contributions and Roth conversions have no income limit. Congress has never closed that gap, and the IRS confirmed in early 2018 guidance that no waiting period is required between the contribution and the conversion. What makes or breaks the result is not the two-step motion itself; it is whether you already own pre-tax IRA money, and whether you file Form 8606 to record the after-tax basis.

Why You’d Use the Backdoor Route

For 2026, single filers can make a full direct Roth contribution with modified adjusted gross income below $153,000, a partial contribution between $153,000 and $168,000, and no direct contribution above $168,000. Married couples filing jointly phase out between $242,000 and $252,000. Above those ceilings, the backdoor is the only path into a Roth IRA.

The annual contribution limit that flows through this strategy is $7,500 for 2026, or $8,600 if you’re 50 or older, and that is a combined limit across all your IRAs.1Internal Revenue Service. 401(k) Limit Increases to $24,500 for 2026, IRA Limit Increases to $7,500

The Clean Example, Step by Step

Return to that $200,000 single filer with no Traditional, SEP, SIMPLE, or rollover IRA balances anywhere. Here is what actually happens across the calendar and the tax return:

  • Monday. You contribute $7,500 in cash to a new Traditional IRA at your brokerage. Leave it in the money market or settlement fund. Do not invest it in stocks or bonds, because gains before the conversion become taxable income.
  • Wednesday. The contribution has settled. The balance now reads $7,500.83 after two days of interest. You click through the brokerage’s Roth conversion function and move the entire $7,500.83 into your Roth IRA.
  • The following spring. You file Form 8606 with your tax return, reporting a $7,500 non-deductible contribution. The $7,500 of basis converts tax-free. The $0.83 of settlement interest is taxable at your ordinary rate. At a 32% marginal bracket, that is roughly 27 cents of extra tax.

The Roth IRA now holds $7,500.83, and it will grow tax-free for decades. You did not claim a deduction for the Traditional IRA contribution, which is what created the after-tax basis that made the conversion tax-free in the first place. Repeat the same two steps every year, and the balance compounds into money you could not have put in a Roth directly.

Zero Out Pre-Tax IRA Balances First

Before contributing a single dollar, check the balance of every non-Roth IRA you own: Traditional, SEP, SIMPLE, and rollover IRAs. The IRS treats all of them as a single pool when it calculates how much of any conversion is taxable.2Office of the Law Revision Counsel. 26 USC 408 – Individual Retirement Accounts You cannot pick out the after-tax dollars and convert only those.

The standard fix is to roll pre-tax IRA money into your current employer’s 401(k), 403(b), or governmental 457(b) before December 31 of the conversion year. Employer plans do not count in the aggregation, so moving the money out of the IRA world removes it from the calculation entirely. Most employer plans accept incoming rollovers; confirm with your plan administrator. Self-employed workers can open a solo 401(k) for the same purpose as long as they have some self-employment income.

Inherited IRAs are not aggregated with your own IRAs for this calculation, so an inherited Traditional IRA at another firm does not interfere. Roth IRAs are not counted either.

What the Example Looks Like When Pro-Rata Bites

Change one fact and the numbers change dramatically. Suppose the same filer has a SEP IRA from earlier freelance work with a $92,500 pre-tax balance. They still contribute $7,500 non-deductibly to a Traditional IRA and immediately convert that $7,500 to a Roth.

The pro-rata formula divides total non-deductible basis by the total year-end balance of all non-Roth IRAs. On December 31, the total across the SEP and Traditional IRA is $100,000, of which $7,500 is after-tax basis. The tax-free percentage is $7,500 ÷ $100,000, or 7.5%. So only $562.50 of the $7,500 conversion is tax-free. The remaining $6,937.50 is taxable as ordinary income. At a 32% marginal rate, that is roughly $2,220 in tax.

The SEP balance did not shrink. Nothing was withdrawn from it. Its mere existence on December 31 forced most of the conversion to be taxable. And the December 31 balance is what matters regardless of when during the year you converted: a 401(k) rolled into a Traditional IRA in October will retroactively change the tax-free percentage of a conversion you did back in February. Plan the whole year before you act.

Form 8606: The Paperwork That Makes It Work

The entire tax benefit hinges on filing IRS Form 8606. The form tracks your non-deductible basis and calculates the taxable portion of the conversion. Without it, the IRS assumes your Traditional IRA was fully pre-tax and taxes the entire conversion.3Internal Revenue Service. Instructions for Form 8606 (2025)

For the clean example above, the form reports:

  • Line 1: the $7,500 non-deductible contribution.
  • Line 2: prior-year basis, which is zero the first time you do this.
  • Line 6: total value of all Traditional IRAs on December 31, which is zero if you converted everything.
  • Part II, Line 16: the total amount converted.
  • Line 18: the taxable portion, which should be zero or the small earnings amount.

The taxable amount from Line 18 flows to Form 1040, Line 4b. Your brokerage will also send a Form 1099-R the following January showing the conversion in Box 1 with a distribution code in Box 7. The 1099-R and the 8606 need to reconcile.4Internal Revenue Service. IRS Form 8606 – Nondeductible IRAs

If pre-tax balances are in play, Part I of the form walks through the pro-rata fraction and splits the conversion into taxable and tax-free portions. Any unused basis carries forward to Line 2 of next year’s Form 8606, and you keep filing the form every year until the basis is fully converted or withdrawn.

The penalty for failing to file Form 8606 is $50 per missed year, waivable for reasonable cause.5Office of the Law Revision Counsel. 26 US Code 6693 – Failure to Provide Reports on Certain Tax-Favored Accounts or Annuities The larger cost of skipping it is paying income tax on money that should have moved tax-free.

Deadlines That Trip People Up

Contributions and conversions run on different clocks, and confusing them can cost a year of Roth funding.

The safest sequence for most people: contribute early in the calendar year, convert within a few days, and avoid rolling any employer plan money into a Traditional IRA for the rest of that year.

The 5-Year Rule on Converted Amounts

Roth IRAs impose a separate 5-year holding period on each year’s conversions. If you withdraw converted amounts within five years and you’re under 59½, the IRS can impose a 10% early withdrawal penalty on the portion that was taxable at conversion.7Office of the Law Revision Counsel. 26 USC 408A – Roth IRAs

For a clean backdoor Roth, the rule has almost no bite. The taxable portion was zero or close to it, and the penalty applies only to that taxable portion. If pro-rata forced a large taxable share into your conversion, the 5-year clock matters more. Either way, backdoor Roth money is meant to sit for decades of tax-free growth, which is where the real payoff comes from.