My boyfriend & I both own a home together, both of our names are on the title, but he pays the mortgage and taxes. Do I claim the house as well if he already did?

[Carl]

No. That would be double-dipping and fraudulent. What I see most often for those in your situation, is where the two tax filers take turns each year swapping the property taxes and mortgage interest - assuming the one claiming each actually paid it of course. This also is assuming this house is the primary residence for both of you, and both of you physically live in it as your primary residence.