I purchased rental property in Dec but only started to rent out in Jan. How can I deduct cost/lose?

If the house was in fact available for rent in Dec, then you can go ahead and report it on SCH E. Some things to point out though.

- Number of days rented "MUST" be at least one day. If you enter ZERO for days rented, you will be "forced" to delete the SCH E.

- Rental income "MUST" have a digit in it. Even if that digit is a round circle ZERO. You just can't leave it blank.

- Yes, it is perfectly possible and feasible to have a property rented for one day in a tax year (dec 31) and still have zero income for that tax year. Zero income is exactly what it would be, if the renter did not pay the rent until Jan 1st, right?

Finally, note that when completing the SCH E for the very first time in that very first year for a rental property, absolute and total perfection is not an option. It's a "MUST". Even the tiniest of mistakes will grow exponentially as the years pass. Then when you catch your error years down the road, if the IRS doesn't catch it first, the cost of fixing it will be high. So ask questions when you're not sure. The only dumb question is the one you never asked. It's not like you learn this stuff through osmosis. I most certainly didn't.

The below information is provided to you, because in my personal opinion (and we all know what opinions are like.) the program does not provide you clarity on some things, that I think it should and would like it to. So I do my best to provide you that clarity here. But even so, if you have questions please ask... or forever lose your wealth to the IRS.

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 "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.

RENTAL PROPERTY ASSETS, MAINTENANCE/CLEANING/REPAIRS DEFINED

Property Improvement.

Property improvements are expenses you incur that “better” the property. Basically, they retain or add value to the property. Expenses for this are entered in the Assets/Depreciation section and depreciated over time. Property improvements can be done at any time after your initial purchase of the property. It does not matter if it was your residence or a rental at the time of the improvement. It still adds value to the property.

To be classified as a property improvement, two criteria must be met:

1) The improvement must become "a material part of" the property. For example, remodeling the bathroom, new cabinets or appliances in the kitchen. New carpet. Replacing that old Central Air unit.

2) The improvement must retain or add "real" value to the property. In other words, when the property is appraised by a qualified, certified, licensed property appraiser, he will appraise it at a higher value, than he would have without the improvements.

There are rules that allow you to just flat-out expense and deduct some property improvements, if the total cost of the improvement was less than $2,500. It’s referred to as “safe harbor di-minimis” But depending on the specific situation, this may or may not be beneficial. Just be aware that not every property improvement that cost less than $2,500 qualifies for this. If this interest you, the rules can get complex. So a good place to start reading is on the IRS website at https://www.irs.gov/businesses/small-businesses-self-employed/tangible-property-final-regulations. The stuff on di-minimis starts about one page down.

Cleaning & Maintenance

Those expenses incurred to maintain the rental property and it's assets in the useable condition the property and/or asset was designed and intended for. Routine cleaning and maintenance expenses are only deductible if they are incurred while the property is classified as a rental. Cleaning and maintenance expenses incurred in the process of preparing the property for rent are not deductible.

Repair

Those expenses incurred to return the property or it's assets to the same useable condition they were in, prior to the event that caused the property or asset to be unusable. Repair expenses incurred are only deductible if incurred while the property is classified as a rental. Repair costs incurred in the process of preparing the property for rent are not deductible.

Additional clarifications: Painting a room does not qualify as a property improvement. While the paint does become “a material part of” the property, from the perspective of a property appraiser, it doesn’t add “real value” to the property.

However, when you do something like convert the garage into a 3^rd bedroom for example, making a  2 bedroom house into a 3 bedroom house adds “real value”. Of course, when you convert the garage to a bedroom, you’re going to paint it. But you will include the cost of painting as a part of the property improvement – not an expense separate from it.