Deductions & credits
Sorry if my point about using 1% was distracting. I only pointed it out to show that TT is able to correctly handle non-zero allocations (even non-zero allocations very close to 0%), but makes a mistake when it encounters a zero allocation. I'd rather not use a 1% allocation as it ends up costing us money.
If I use a 1% allocation for Jan - Aug, TT calculates small PTC repayment amounts for those months, and the correct (larger) repayment amounts for Sept to Dec. In that case the 8962 amounts are calculated at a 1% allocation for Jan to Aug and a 100% allocation for Sept to Dec.
But changing to a 0% allocation for Jan to Aug zero's out all months of the PTC repayment, including the PTC repayment for Sept to Dec. This is incorrect as I do owe the Sept to Dec PTC repayment. (Since the other tax family was not covered by this plan from Sept to Dec, the Sept to Dec PTC repayment would not be repaid by them.)
This can be tried in the scenario you tested by including premiums for all twelve months and then adjusting the income to be high enough so that the maximum premium assistance is less than the monthly advanced PTC. At a 1% allocation for Jan to Aug, the repayment would be small for Jan to Aug and larger for Sept to Dec. Here's what that looks like:
1095-A:
Adjusting income so that my monthly contribution is $645, this generates the following 8962. Notice that Jan to Aug results in small PTC repayment amounts, while Sept to Dec results in larger PTC repayment amounts:
If I then change the Jan to Aug allocation from 1% to 0%, the following is the resulting 8962. Note that there is no repayment shown (and is blank for all values):
What I expected for the 0% allocation was zero's for Jan to Aug, and non-zero numbers for rest of the year (the Sept to Dec numbers for 0% should be the same as the Sept to Dec numbers for 1%).
