Form 4684 is used to report casualties or thefts of personal-use property, business property, or income-producing property. The deductible loss is usually the difference between the fair market value of the property before the casualty or theft and the fair market value after the casualty or theft but this loss in value must be reduced by (1) reimbursements received for the loss and (2) if the property was used for personal purposes, by the $100 floor (18.12). However, the loss may not exceed your adjusted basis (5.20) for the property, which for many items will be your cost. If your adjusted basis is less than the loss in value, your deduction is limited to basis, less reimbursements and the $100 floor for personal-use assets. After figuring all allowable casualty and theft losses and gains for personal-use property, the net loss (losses in excess of gains if any) is deductible only to the extent it exceeds the 10% adjusted gross income (AGI) floor (18.12).