Money & investing · 4 of 6
Backdoor Roth IRA: A Step-by-Step Walkthrough
How to fund a Roth IRA when your income is over the limit: the contribution, the conversion, the pro-rata rule, and Form 8606, step by step.
Informational only
This guide explains the mechanics of the Backdoor Roth strategy and does not constitute tax or financial advice. The Pro-Rata Rule requires careful evaluation of your specific IRA balances. Consult a CPA before executing.
What this guide covers
The Backdoor Roth IRA is a two-step process that lets high earners make Roth contributions indirectly. The key numbers for 2026:
The Pro-Rata Rule: the one thing you must get right
Before executing this strategy, you need to understand the one rule that can make the entire conversion taxable. The IRS does not let you cherry-pick which IRA dollars you convert. It treats all your Traditional, SEP, and SIMPLE IRA balances as a single pool.
If you have $92,500 in a pre-tax Traditional IRA and contribute $7,500 post-tax, your total IRA pool is $100,000. Only 7.5% of any conversion is treated as post-tax. Converting $7,500 means $6,938 is taxable, the opposite of what you intended.
✓ Clean conversion (what you want)
Your Traditional, SEP, and SIMPLE IRA balances total $0 before you contribute. Your $7,500 is 100% post-tax and the conversion triggers no additional tax.
✗ Pro-Rata problem (what to avoid)
You have any pre-tax IRA balance, including rollover IRAs from old 401(k)s. The IRS calculates the taxable portion proportionally across all IRA funds, making the strategy largely pointless.
How to clear pre-tax IRA balances
If you have rollover or Traditional IRA balances from old jobs, you have two options:
- Roll into your current employer’s 401(k). Most modern plans accept incoming rollovers. This removes the balance from the IRA system entirely.
- Roll into a Solo 401(k) if self-employed. SEP-IRA and SIMPLE IRA balances can also be moved this way.
Step-by-step walkthrough (Vanguard)
The mechanics are identical at any major brokerage. This walkthrough uses Vanguard; Fidelity users will find the process nearly identical with slightly faster settlement.
Contribute to a non-deductible Traditional IRA. Go to your Traditional IRA and contribute $7,500 (or $8,600 if 50+). When asked about deductibility, select non-deductible. This is a post-tax contribution: you get no tax break now, but you won’t be taxed again on withdrawal.
Wait for settlement (2–3 business days). The funds land in a money market settlement account first. Do not buy securities during this window. Any gains, even $0.12 in interest, create a small taxable amount at conversion. Waiting keeps the conversion clean.
Convert to Roth IRA. Find the “Convert to Roth IRA” option (on Vanguard: Transact → Convert to Roth IRA). Transfer the entire balance. When asked about tax withholding, select 0% (do not withhold taxes). Withholding reduces the amount converted and creates a taxable event.
Invest the converted funds. Once the conversion settles in your Roth IRA (usually same-day), allocate to your target index funds or ETFs. You’re done.
Tax reporting: Form 8606
Every year you execute a Backdoor Roth, you must file IRS Form 8606 with your tax return. This is non-negotiable. It’s the mechanism that prevents the IRS from taxing your conversion again at withdrawal.
Part I: Non-deductible contributions
You report the non-deductible Traditional IRA contribution here. This establishes your “basis,” the post-tax amount that won’t be taxed again on withdrawal. If you skip this form, the IRS has no record of your basis and may tax the entire conversion.
Part II: Roth conversions
You report the conversion amount here. Because your basis equals the conversion (clean $0 pre-tax IRA scenario), the taxable amount should be $0, or a small number if you earned interest during settlement.
Store copies of every Form 8606 you ever file. They document your cumulative IRA basis. If records are ever lost or disputed, the form is your proof that you already paid tax on those funds.
Common mistakes
Forgetting to check IRA balances first
The most common error. People execute the conversion without realizing an old rollover IRA exists, often from a 401(k) at a job held years earlier. Check all IRA accounts at all brokerages before contributing.
Withholding taxes from the conversion
If you withhold 10% from a $7,500 conversion, only $6,750 ends up in your Roth. The $750 withheld is treated as a distribution, potentially subject to the 10% early withdrawal penalty if you’re under 59½, plus income tax.
Buying securities before converting
If you invest the Traditional IRA funds and they gain before conversion, the gain is taxable at conversion. Keep the funds in cash (settlement/money market) during the window between contribution and conversion.
Not filing Form 8606
Without this form, the IRS treats your entire conversion as taxable. The penalty for not filing is $50, and failing to document your basis compounds every year you skip it.
Annual Backdoor Roth checklist
Backdoor Roth execution checklist
Frequently asked questions
Who needs the Backdoor Roth IRA strategy?
What is the Pro-Rata Rule and why does it matter?
Does the Backdoor Roth trigger taxes?
Can I do this at any brokerage?
Cite this guide: "Backdoor Roth IRA: A Step-by-Step Walkthrough", jason.guide, updated 2026-10-11. https://jason.guide/guides/backdoor-roth