Improvements to a property in prior year before I began renting it out

[Eric D]

I bought a single family home in 2015.   In 2018 and 2019, I completed improvements (building a accessory dwelling unit).  In August 2019, I began renting out the main house and I lived in the Accessory dwelling unit.  What improvements can I list as a deduction?  Can I use what was spent in 2018?  Or do I simply have zero improvements since the house was not for rent when I was completing them and instead just have a higher depreciation value?

[LeonardS]

The portion of your improvements that are considered to be a capital improvement will be add the adjusted cost basis of the property regardless of its use.  A capital improvement will either enhance the property's overall value, prolongs its useful life, or adapt it to new uses.  If it does not meet the criteria for being a capital improvement, then it would be considered a repair expense.  The repair expenses incurred prior to rental use are not deductible.

[Eric D]

Since this should be a capital improvement before being turned into a rental, would I take the assessed property value and add the improvements cost, or instead use the new property tax assessment value?  The first option is a higher value.