What a backdoor Roth conversion actually costs you in tax. Most explanations tell you the pro-rata rule exists; this computes the fraction of your conversion the IRS will treat as taxable, and what that comes to in dollars.
The pro-rata rule aggregates every traditional, SEP and SIMPLE IRA in your name, at every custodian, measured on December 31 of the conversion year. That is why people get this wrong: they check the account they are converting from, see only the new contribution, and conclude the conversion is clean. An old rollover IRA at a former employer’s provider counts. A 401(k) does not.
What moving actually saves, on your own income mix rather than a headline rate — and how to establish domicile so the state you left cannot follow you.
Which account to draw first, priced. The three cliffs a withdrawal can cross without warning, the conversion window almost nobody uses, and why the order is the last big decision you can still change.