S-corp tax filing for uber and flipping house(3 years held)

[Earl Stewart Jr]

I have a single member LLC that is taxed as a S-Corp in which I flip homes and drive for Uber. I purchased a property in 2017 and finally sold it in 2020. I sold it for less than what I bought it for. I have filed the 1120s each year but I never included the expenses and writes offs for the property. The 1120s just reflects the income and deductions for Uber. Now, that the property is sold, I am aware that I need to figure out my cost basis and account for all the property's expenses, closing costs, etc. A previous CPA told me to not write off any expenses for the property until it was sold because it would help offset the capital gain from the sale. Except, it's a capital loss for me. Now, I have 2017-2020's expenses to account for on this year's taxes. The property was sold for $60,000 less than the purchase price. My situation is sort of complicated because of everything that has happened. The CPA who I was using did some bad stuff so I am just trying to figure out this dilemma the best I can. Thanks

Do I still need to account for cost basis even though I sold the property for less?