It depends. The decision is between you and your girlfriend. My suggestion would be to look at how you both would benefit the best.
- If you claimed the entire amount along with the property taxes and any charitable donations or medical that you might be eligible to take and that total is more than the single standard deduction of $12,500 then maybe you take the full amount of the deduction.
- If your girlfriend would, if claiming the full amount of the mortgage interest, property taxes, etc. and she would have more than $12,500, then maybe she takes the full amount of the deduction.
- Since you are both on the mortgage, you could split the mortgage interest and property taxes and along with any other deductions would add up to more than the single standard deduction of $12,500 then you could split the deduction.
- It is possible that neither one of you can claim the deduction since neither of you has more than $12,500 in deductions and you would both take the standard deduction.
If you are going to split, you would each claim one-half of the mortgage interest and one-half of the real property taxes.
The first thing I would do is for you to add the amount of the mortgage interest and real property taxes and see if it would bring either one of you anywhere near the $12,500 of the standard deduction. This may be a moot point since neither of you may be able to claim the deduction.
