How does the pro-rata rule affect a backdoor Roth IRA?
The pro-rata rule is the reason a backdoor Roth is rarely tax-free for someone who already holds pretax IRA money. It prevents after-tax basis from being converted in isolation.
The governing calculation looks at your after-tax basis relative to the total value of your traditional, SEP and SIMPLE IRAs. Whatever proportion of that total is pretax is the proportion of the conversion that is taxable — no matter which account the converted dollars actually came from.
Separate account statements do not create separate tax treatment, and waiting between steps does not change the result. Only a change in what the calculation counts can do that.
Reviewed by Bay Area Wealth Advisors. Last reviewed 2026-09-16. Educational information only — not individualized financial, tax or legal advice.