If you have a space in your home that you use regularly and exclusively for
business, you may qualify for home office deductions. That will be true if
this office is your principal place of business, including a sideline business.
You also can qualify if your office is in an unattached structure, such as a
room over a garage.
Say your home office takes up one room out of 10 rooms in your home, or
that it occupies 10 percent of the floor space. You can depreciate 10 percent
of your home. You also can deduct 10 percent of your costs of insurance,
home security, utilities, etc. In order to support a home office deduction:
Install a separate business phone in the office.
Use your home office phone number on business cards, stationery, and
advertising.
Have your business visitors sign a logbook.
Keep written records of the time spent in your home office.