It took me a while to follow the yellow brick roads, but I think @MaryK4 is correct, and it works like this:
- Premiums for marketplace plans are entered as Personal deductions in the Medical section. The unsubsidized premium totals (Column A) get moved to Schedule 1, line 17.
- Premiums for Medicare Part B and medigap plans are entered as Business expenses (in the "Other Common Business Expenses">"Insurance Payments" section). The total premiums paid for these plans appears as a sub-entry on TT's Schedule C, line 15, but is not used anywhere on Schedule C. (The IRS's Schedule C has no such sub-entry.) The value there is combined with the premium total for the marketplace plans, and the result is that Schedule 1, line 17, contains the sum of the premiums for my two marketplace plans, Medicare Part B, and my medigap plan.
Such fun!
