Casualty and Theft losses are reported on IRS Form 4684 for both personal and business. See IRS tax topic - <a rel="nofollow" target="_blank" href="
https://www.irs.gov/taxtopics/tc515.html">https://www.irs.gov/taxtopics/tc515.html</a>
However, claiming a theft loss without filing any type of police report or insurance claim for proof of loss would more than likely be denied by the IRS if ever questioned about the loss.
