My partner and I purchased a home together in 2016, we are both on the mortgage, and both listed on the 1098 (though I'm listed first).  My question goes to allocation of the house-related deduction (interest, PMI, taxes).   We pay via a shared account, some months 50/50, some months differently based on other expenses that come up for maintenance, etc. and who pays for those expenses.   Should we stick to the 50/50 allocation of the deductions, or actually add up the amounts each contributed for the year, and get a ratio? It seems like 50/50 would be the most straight forward. 

Thanks in advance.