If you have a casualty and/or theft loss on property used 100% for business, you will report the loss on Form 4684 Casualties and Thefts, in Section B for business property. You will need to enter this through the Business Income topic of the Federal Q&A.
To enter or review business casualty/theft losses:
Once this information has been entered, your loss will carry to Line 14 of Form 4797 Sale of Business Property. Your total gain/loss will then be carried to Line 4 of Schedule 1 (Form 1040) Additional Income and Adjustments to Income.
Note that any link in the information above is updated each year automatically and will take you to the most recent version of the document at the time it is accessed.