When jointly owned property is burglarized or another related type of incident occurs, it is important to understand how the losses apply to each co-owner. The rules that apply to this sort of situation are clearly outlined below. 

Where the same casualty damages co-owned property (other than property owned by spouses), the $100 (or $500 for qualified disaster losses) floor applies separately to each person. In general, one joint owner can’t have a theft loss deduction for jointly owned property taken by the other joint owner, since the latter has a right to possession. However, if the other owner can show that he/she has a superior interest in the property, a theft loss between owners may be allowed (Dandeneau, Alice, (1971) TC Memo 1971-128).

Note: For years 2018-2025, per the TCJA, the only deductible personal casualty losses are those incurred in federally declared disaster areas.