If you are not legally married you cannot file together. You would file separate returns as Single or Head of Household, whichever you qualify for. Only one person can file as Head of Household. Only one of you can claim the child. The information for your home, you can share, the sum of the two must equal to the total of mortgage interest and property taxes. You cannot each claim the total. The split does not need to be 50/50.
Head of Household filing status qualifications:
1. You are not married or “considered unmarried” on the last day of the year. You are considered unmarried if you lived apart from your spouse the entire last 6 months of the year.
2. If "considered unmarried" you file a separate return from your spouse.
3. You paid more than half the cost of keeping up your home for the year.
4. You have a qualifying child (whether or not you claim the dependency exemption) or you claim a dependency exemption for a “qualifying person” who is related to you and who lived with you in the home for more than half the year. An exception is a parent does not have to live with you to be a qualifying person.
