Check to see what the value is on line 12b of your form 1040.
IF that $$ amount is the same as what the IRS indicates is your tax....then, in order for TTX to have a zero on line 16, there would have to be a value on line 13b which zero'ed out your tax for some type of tax credit. The IRS may be having a problem with the line 13a or 13b value.
But that's a guess, since figuring the details out in this public forum are unlikely.
____________*Answers are correct to the best of my knowledge when posted, but should not be considered to be legal or official tax advice.*
