I'm reporting back to say that the TurboTax calculations for federal and state do indeed appear to be using your current MAGI to calculate your ACA credit, then subtracting that from the monthly enrollment premiums (1095-A column A minus the total credit you qualify for). This represents what you should have paid for your Marketplace plan, not what you actually paid (that would be 1095-A column A minus column C).
I underestimated what I would make in 2025, and have to repay some of the premium tax credits; this discrepancy, combined with the use of an advanced algorithm in TurboTax, meant I was seeing very different numbers than what I thought should be there.
But I suspect I may be an edge case for several other reasons as well... my earned income from self-employment was less than the cost of my premiums, so I had to go back and answer No to the question that asked if I was self-employed and bought a Marketplace plan. However, this ensured that I qualified for the Missouri health insurance premium deduction (because I wasn't taking a federal one), and TurboTax automatically filled in that box with the correct amount (1095-A column A minus the total credit I qualify for).
I did make enough from self-employment to cover the cost of my dental insurance (which was purchased on the Marketplace, but no credits apply), so I entered that as a separate health insurance premium expense for my business. Every little bit helps!
Anyway, I wanted to report back in case any of this helps those who might be in a similar situation. Good luck!
