I no longer comment on how TurboTax calculates the SEHID when PTCs are involved. The IRS says that you can use any reasonable method that ensures that sum of the SEHID and the PTC does not exceed the cost of the health insurance and that the PTC is correct given the the AGI that results from the SEHID. TurboTax's calculation that follows the IRS guidance in IRS Pub 974 ensures that, but might not be optimal when the iterative calculation does not converge.
