If it's related to business activities, such as rental property, it's deductible. Complete Form 4684.
If this was personal, it's doubtful that the loss is deductible. A recent IRS ruling states that for a theft loss to be deductible, the transaction must be one entered into for profit. The taxpayer's motive determines whether the transaction qualifies as profit-oriented.
ccm 202511015
https://www.irs.gov/pub/irs-wd/202511015.pdf
