You may have to recapture depreciation if you took any Sec. 179 depreciation, Sec. 168(k) bonus depreciation, or if you used MACRS for your depreciation method. Essentially, you need to recalculate depreciation as if you used the straight-line method the entire time. This will be treated as a disposition on Form 4797 and any depreciation recapture calculated will carry to your 1040 as ordinary income. See page 60 of Publication 946 for an example and more information.
