This is flipping incredible. @Nicholas Aiolayou are a saint. The root of this question is this, what does one do when significantly too much depreciation has been claimed in previous tax years by mistake on a property that was sold this tax year? I'll add that this situation has been communicated to a local CPA/attorney for assistance and the plan is to hire this out but am asking here for additional background and understanding because I had not idea what the answer should be.
If you are curious, the background of the question is this: The depreciable basis for a condo that was sold in 2017 was calculated incorrectly from the it was used as a rental which started in 2009. The owner owned 50% of the condo but by mistake depreciated it as if 100% was owned, meaning that too much depreciation was claimed. I'm not sure who or how the mistake was made but looking at the tax returns it looks to me like that is what happened and at this point how it happened is irrelevant. Also, the gain on the sale will look like a loss because by basis was entered as 100% of the purchase price, rather than the correct 50%. The property was sold for a gain but not so much or a gain that my 50% stake in the sale is larger than 100% of the purchase price. What needs to be done here? File amended returns going back the 9 years since it was converted to a rental? I have read online that from 3115 and 481(a) might be required, whatever that means.