Investors & landlords

Re a rental apt. I took building depreon  ciation the first year  (2003) I put my property in service, using Turbotax  software. I never took  depreciation after that. In the following years from 2003 to 2018, I was relaying the Turbotax program to complete the tax return, and somehow I missed that. How can I make correction and how many years I can go back?

Thank you