
Form 8606 and the Backdoor Roth: How One Missing Tax Form Causes Double Taxation
Form 8606 is the IRS's running ledger of after-tax basis inside traditional, SEP, and SIMPLE IRAs. Skip it and the IRS treats your basis as zero, taxing the same dollars a second time at distribution. This guide explains how the form works, why the pro-rata rule punishes most backdoor Roth conversions, and how to keep your basis documented for the next 30 years.










