Was the property actually "available for rent" on or before Dec 31 of the tax year? If it was not, then you don't report this on SCH E on your 2020 tax return at all. Not a single penny. You'll deal with it on the 2021 tax return you'll complete next year.
Assuming the property was available for rent on or before Dec 31 of the tax year, the below information applies.
Rental Property Dates & Numbers That Matter.
Date of Conversion - If this was your primary residence or 2nd home before, then this date is the day AFTER you moved out, or the date you decided to lease the property – whichever is later.
In Service Date - This is the date a renter "could" have moved in. Usually, this date is the day you put the FOR RENT sign in the front yard.
Number of days Rented - the day count for this starts from the first day a renter "could" have moved in. That should be your "in service" date if you were asked for that. Vacant periods between renters count also PROVIDED you did not live in the house for one single day for any type of personal pleasure use during said period of vacancy.
Days of Personal Use - This number will be a big fat ZERO. Read the screen. It's asking for the number of days you lived in the property AFTER you converted it to a rental. I seriously doubt (though it is possible) that you lived in the house (or space, if renting a part of your home) as your primary residence, 2nd home, or any other personal use reasons after you converted it to a rental.
Business Use Percentage. 100%. I'll put that in words so there's no doubt I didn't make a typo here. One Hundred Percent. After you converted this property or space to rental use, it was one hundred percent business use. What you used it for prior to the date of conversion doesn't count.
If you closed on the purchase on Dec 23, and on that same day put a "FOR RENT" sign in the front year (and the property was actually move-in ready) then the property was rented "the whole year". The fact you have no rental income for 2020 *does* *not* *matter* one bit.
