@DN76 wrote:
Ok and in terms of the audit, would it matter if you had payments coming in to your account from your girlfriend to cover their 50% share, so long as it was your personal account and you were the one paying it?
You can claim a deduction for what you actually pay. If audited, you need to prove this to the examiner, and we don't have any special insider information on what kind of proof the examiner would like to see.
It would seem fair to me that if you pay the mortgage from a joint bank account that you each contribute to equally, the logical conclusion is that you each paid half the mortgage. I don't think it should be necessary for you and your partner to each write separate checks each month for half the mortgage. However, if you did write separate checks for half the mortgage, that would be even stronger proof than paying from a joint account that was jointly funded.
(If your partner paid into your individual separate account and you paid the mortgage, that would be the weakest of the three situations, since you could be asked to prove that the partner was reimbursing you for the mortgage and not for food, travel or other expenses.)
Then as @TomD8 notes, only one SSN will be on the 1098. That person enters the 1098 but claims half the mortgage. The other person checks the box for "I did not get a 1098" and claims the other half, and includes an explanation.
