it was rented from September to December 2020.
So roughly, 4/12 of your property taxes, mortgage interest and property insurance are a SCH E expense *PROVIDED* you actually paid that expense in tax year 2020. Understand that expenses are claimed in the tax year they are paid, regardless of what tax year they pay "FOR".
For the mortgage interest and property taxes, the program does a pretty good job of doing the splits itself, allocating the property amount to the SCH E for the period of time the property was a rental, and the SCH A for the period of time it was personal use.
However, the property insurance doesn't work that way. You'll have to pro-rate that yourself. For the percentage of time it was a rental in 2020 you can claim an equal percentage of the insurance that you paid in 2020 *REGARDLESS* of the actual period of time that insurance policy covers. But the percentage of insurance for the period of time the property was *not* a rental, is just flat out not deductible at all, anywhere on your tax return.
For all other expenses, you should only be entering those expenses incurred "AFTER" you converted the property to rental property.
