I bought new air conditioning for a free-standing building on my residential property that I use as a home office. Where do I list that expense?

You can depreciate the air conditioning as an improvement to your home office, that is for your home office alone, and not for the entire house, because this is a free-standing building on your property. 

• When you go through the home office section of TurboTax Self-Employed, you will check that you have expenses that are just for the home office. 
• As you continue, when you reach the depreciation section, check that this is a home office asset that is an improvement to the home. 
• Then enter the cost on Tell Us About This Home Improvement.
• Next, on Tell Us More About This Asset / Large Purchase, check that this is used 100% for business because it is an improvement to the home office only, not the entire home.
• You will then see this entered on the Home Office Asset Summary

See the screenshots below