You both must file as single if you are not legally married. (if there are any dependent children then one of you could file as head of Household). You cannot file a joint return unless/until you are married. If you own the home together--both names on the mortgage and deed, then you can choose to split the amount you each enter on your tax returns for it if you each paid mortgage payments and property taxes, etc. If the home purchase was late in the year ("just purchased....") the deduction is unlikely to do much for either of you. Unless you have enough itemized deductions to exceed your standard deduction, the home ownership entries will not have any effect. You could try using desktop software to prepare your returns with one or the other of you claiming all of the home deductions to see if it works better that way for you.
There is not a first time home buyers credit on a Federal return. That ended in 2010. If your state has such as credit, you will be able to enter it when you prepare your state return.
Buying a home is not a guarantee of a big refund. Your deductions for homeownership combined with your other deductions (if any) must exceed your standard deduction to change your tax due or refund. If you purchased your home late in the year, you do not even have a full year of home ownership deductions.
Go to Federal> Deductions and Credits> Your Home to enter mortgage interest, property taxes, and loan origination fees (“points”) that you paid in 2017. You should receive a 1098 from your mortgage lender that shows this information in January.
Your closing costs on your new home are not deductible except for prepaid interest, prepaid property tax or loan origination fees. There are no deductions for appraisal, inspections, title searches, settlement fees. etc.
Your down payment is not deductible.
Your homeowners insurance for fire, hazard, flood, etc. is not deductible for your own home.
Home improvements, repairs, maintenance, etc. for your own home are not deductible.
Homeowners Association (HOA) fees for your own home are not deductible.
what happens if each unmarried domestic partner in this case normally files head of household with each having a qualifying dependent child, but purchased home together & both names on deed/title; does one need to change their filing status although there's a verbal agreement with the child dependency filed each year?