Thank you @Carl for a very detailed answer. Than you @Critter. Like Carl said, yes, TT will probably take care of the complexity thru easy-step process.
I was trying to understand the details for my satisfaction. Let me take an example and advise if I got it right.
Example: Assume the rental property was bought for 500,000 in 2010, and sold in 2019 for 450,000. Assume sale exp zero. Capital improvements done over the years 50,000. Depreciations on the building/content "allowed" were say 150,000 for the years. Depreciation carryover cumulative balance 2019 = 100,000.
Cost basis = 500,000 + 50,000 = 550,000
Gain = 450,000 - (Basis - Depreciation-allowed) = 450,000 - (550,000 - 150,000) = 50,000
1031 non-recaptured losses/carryovers = 100,000
Net gain (loss) = 50,000 - 100,000 = (50,000) loss that can be taken against ordinary income
