Hopefully, you have all your paperwork for however many years back you didn't report the rental income/expenses/depreciation. Overall, you need a tax professional. Mainly because you didn't take depreciation for 2 or more consecutive years. With that, the only option is the 3115-Change in Accounting Method. A tax pro may be able to help with claiming your Passive Activity Carryover Losses, which along with depreciation, come into play in the tax year you sell.
