Looking to claim a home office deduction, you need to complete IRS Form 8829, Expenses for Business Use of Your Home. The form and instructions for it can be downloaded from the IRS Web site. The form requires a business owner to compute the amount of space in a home that’s devoted to business (exclusivity). In addition, there are separate lines for entering various expenses such as rent, repairs, utilities and mortgage interest.
Form 8829 should be filed only by business owners who attach Schedule C, Profit or Loss from Business, to their Form 1040s. Read Publication 587 (2009), Business Use of Your Home for more information.