When you have a 2000 square-foot house and a 400 square-foot home office, the office space is 20% of the total area of your house. How much of your house can you write off for business? Your home ...

For example, if your home office is one-tenth of the square footage of your house, you can deduct 10% of the cost of your mortgage interest or rent, utilities (electric, water and gas) and ...