If the loss occurred in 2017 and it’s a personal loss, it may be deductible as a theft loss. The loss is treated as an itemized deduction allowable only to the extent it exceeds 10% of adjusted gross income. Starting in 2018, there is no deduction allowed for personal theft losses. Of course, business losses continue to be deductible.
Rules for determining whether a person is active in a business activity for passive activity rule purposes. Unless the tests are met, passive loss limits apply.