Inherited IRA: Caution: TurboTax is using basis for a non-inherited IRA held by same person.

Unfortunately this problem (or something similar) still persists in the online version. If you take distributions from both an inherited IRA with no basis, and a regular IRA with a basis, then they both get blended together in worksheet 1-1.

Workaround: When asked for 'Total 12/31/20 value of all your "Traditional IRAs"', as long as you *exclude* inherited IRAs from your response, the inherited IRA won't screw up the cost-basis and you'll (apparently, based on a review of the 8606) get the right result.