see a tax pro. you have to recapture and pay taxes on the depreciation you should have taken. the pro can help you with form 3115 which will allow you to claim on the 2020 return the depreciation you should have taken. the tax on the depreciation you have to recapture can be at a different rate than the taxes on the deduction you'll get by filing the 3115. do not ignore this. in the worst-case scenario the IRS will catch that no depreciation was taken and bill you. they probably will not help you modify the return to use form 3115 and if it's several years down the road you may lose the ability to ever claim a deduction for the depreciation you should have taken.
