are you now on the deed? if not there is a concept of equitable ownership.
You may be an equitable owner entitled to deduct your share of the mortgage interest and real estate taxes. An equitable owner is a person who has the economic benefits and burdens of ownership, based on the facts. Occupying and maintaining the home and paying the mortgage and taxes on it are (strong) factors that probably would indicate equitable ownership. An equitable owner can deduct interest paid on a mortgage even if they are not directly liable on the debt. IRS REG. 1.163-1. Further, mortgage payments and taxes paid from a joint account with two equal owners are presumed to be paid equally by each account owner (absence evidence to the contrary). However, if payments are made from separate funds, each taxpayer is entitled to deduct all the interest and taxes they pay with their separate funds (CCA 201451027).
* so if you are now on the deed there is no question you can deduct your share of the mortgage interest - see bolded above. the same would be true if you are not but comply with the EO doctrine above.
* to would only enter your share of the amounts - portion of the mortgage balance, interest paid, taxes paid.
* are both of you on the 1098 or do you get separate 1098s - to avoid correspondence from the IRS due to non-matching issues
