Advanced premium tax credit repayment and American Opportunity credit stacking

[user17749907019]

I'm a bit confused about how credits stack. I have an amount of advanced premium tax credit that I have to repay, but otherwise I have no tax due. Normally, if you have no tax bill, the larger piece of the American Opportunity tax credit wouldn't apply, I thought, because it's not refundable, so if you have a tax liability of $0, you can't take that credit. However, because I have an APTC repayment amount from schedule 2, suddenly I can take the full AOTC. It seems that if I had correctly estimated my income and had no APTC to repay, I would not have been able to take most of the AOTC. Am I missing something? Does this make sense? I understand that the APTC is refundable, but as is $1000 of the AOTC, but it's the rest of the AOTC stacking with the APTC repayment that is confusing me.

[MaryK4]

The APTC repayment is treated as a tax and is added to your total tax liability.  The nonrefundable AOTC can be applied to tax due so the stacking is okay.  

When you have to repay the Advanced Premium Tax Credit (APTC), the IRS doesn't just ask for the money back as a separate bill; it adds it to your Total Tax on Form 1040, Line 16 (via Schedule 2).  Because the APTC repayment increased your tax liability from $0 to $1,500, you now have a "bill" that the non-refundable $1,500 portion of the AOTC can be applied against.  If you had correctly estimated your income and had no APTC repayment, your tax liability would have stayed at $0.

[user17749907019]

I agree that's what the form seems to say, but to me it doesn't make sense. 
Say I should be allowed $15000 of PTC.

Case 1: I use $15000 of PTC in advance of doing my taxes. My tax liability is 0. I can't collect the (nonrefundable portion of the) AOTC. My total gain in credits is $15000 plus the $1000 refundable piece of the AOTC.
Case 2: I use $16500 of PTC in advance of doing my taxes. I have to pay back $1500, but that makes it so I can claim the nonrefundable portion of the AOTC, reducing the amount I have to pay back to zero. My total gain in credits is $16500 plus the $1000 refundable piece of the AOTC. 

This doesn't make logical sense to me! Is there something I'm missing?

[NCperson]

@MaryK4 can you please review your response?  I think you note the incorrect line item. 

@user17749907019 

The PTC repayment occurs on Sch 2 / line 1a. The sum of the taxes in this section maps to Form 1040, Line 17 and that adds to the non-refundable section of the tax return.

The non-refundable portion of AOTC occurs on Sch 3 / line 3.  The sum of this section maps to Form 1040, Line 20 and that subtracts from the non-refundable section of the tax return. 

While it may not be logical, it's how Congress passed the law.  I wouldn't presume Congress is always logical.