Part of the calculation for depreciation is a table for entering the percentage of use for individual months, depending on which month you first used your home for business during the year. For example, if you first used your home in January, enter 2.461% (the maximum), but if you only started using your home for business in December, enter 0.107% (the minimum). You can find the table on page 5 of the Instructions for Form 8829.