As you (hopefully) know, if you are a homeowner, you can deduct your property taxes, mortgage interest, and if applicable, mortgage insurance. You will receive a form from your mortgage company in January showing the amount of interest paid. If you’re unsure about your property tax payments, you will probably be able to look them up online at the County Assessor’s website. If you just purchased a house this year, hold onto your closing papers, because there are often payments for interest and taxes listed there.
There might be other things you can deduct, depending on your situation.
If you work from home and have a home office or studio, you can deduct utilities, homeowner’s insurance, maintenance and repairs, as well as a portion of the cost of the house and most major improvements (e.g. replacing the roof, fixing the foundation, an earthquake retrofit).
The same goes for if you rent out a portion of your house.
The best (and most common) way to allocate these costs is on a per-square-foot basis.