Why would rental property depreciation on Form 4562 only shows a small fraction of the amount, compared to the actual cost basis (minus land)? ~83k vs 210k

[bparikh18]

This is a new rental property for 2020.

[Mike9241]

for real property, there is the mid-month convention. so first divide the building cost by 27.5 for non-commercial or 39 for commercial   to get the annual depreciation 

then

you treat property placed in service at the midpoint of the month. This means that a one-half month of depreciation is allowed for the month the property is placed in service

here's a link to PUB 946 look at table A-6 or A-7a for the first year depreciation factor

https://www.irs.gov/pub/irs-pdf/p946.pdf 

[Carl]

Why would rental property depreciation on form 4562 only shows a small fraction of the amount,

What are you calling a small fraction? What are you expecting? Residentail rental property is depreciated over 27.5 years. Therefore, only a small fraction gets depreciated each year. For the first year, depending on the month placed in service, the depreciation allowed/taken can be even less if the property was placed in service at some point other than 1-15 Jan of that tax year.

Also, assuming you're working 2020 taxes and further assuming that 2020 is the first year you placed the property in service, it's highly likely you entered incorrect information, as for some of the data entry screens lack the clarity needed to ensure you make the correct selections and enter the correct data.For example, if you placed the property in service on Jun 1, 2020, yet you stated the property was rented less than 100% of the time, that would be wrong in most cases (*NOT* *EVERY* *CASE*, but possibly in your case.)

So you make want to work through the property profile again after reading the below information.

Rental Property Dates & Numbers That Matter.

Date of Conversion - If this was your primary residence or 2^nd 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 was contracted to move in, and/or "could" have moved in. That would be your "in service" date or after if you were asked for that. Vacant periods between renters do not count for actual days rented. Please see IRS Publication927 page 17 at https://www.irs.gov/pub/irs-pdf/p527.pdf#en_US_2020_publink1000219175 Read the “Example” in the third column.
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.

[AmeliesUncle]

You need to indicate it was 100% for business.  Do NOT reduce the percentage based on the partial year (the "placed in service" date already prorates it).