On a U.S. Federal tax return, you can write off interest and property tax payments on a mortgage. Who gets to do that? Just the person in whose name the mortgage is? Or anyone on the title of the property?
The name on the Form 1098 that the mortgage lender sends you. That's the SSN and payments reported to the IRS.
The person who both (a) is on the mortgage and (b) pays the mortgage.