Can I add swimming pool to the cost basis of a rental property started in 2016 and sold in 2018 in the year it was first put into rental. Pool installed 2015.

[raypacella]

I placed a former primary residence into a rental in 2016 and started to depreciate the property that year.  I sold the property in 2018.  However, I forgot to add the cost of the swimming pool I installed in 2015 as part of my cost basis on my 2016 tax return.  Can I add the pool on my 2018 tax return, with an install date prior to 2018, that will increase my cost basis or do I need to amend my 2016 and 2017 tax returns first, showing the increased cost basis which includes the pool? 

[CarolynM]

Yes, you can add the value to your cost basis because the pool is an improvement to your rental property.