In my particular case, I had a value on Line 29 of 8962. To get the math to match TurboTax, I had to take wsparrowhood's "Step 1" amount and ADD it to the "Step 2" amount. NOTE that TT fills in the form 8962 by rounding EACH month up or down as appropriate from the values you enter into the 1095-A. Compare your 1095-A actuals to TT's form 8962 entries and you'll note this to be true. It's the TT rounding that is throwing us all off a few bucks up or down. Right clicking on the value TT places at line 2b of the Medical Expenses worksheet and then hitting "Data Source" brings up a dialogue box that tells you more about how TT does the math.
