We have owned our home for 9 years. My wife has run a child daycare in our home for the entire time. I have never taken the deduction for depreciation of our home (form 8829). My understanding is that the depreciation rate is 2.564% per year. My question is, can I go back and take the depreciation for the previous years on this years return (2.564 x 8 = 20.512%) or can I only use the one year 2.564% as my depreciation rate?