if you use the cash basis you have already written off their cost. If you account for inventory the deduction will be taken through the cost of good sold because ending inventory won't include those items. if you received insurance proceeds for this in the same year as the fire, you'll need to reduce a cost/expense somewhere. if in a subsequent year this would need to be reported in the year received as other schedule C income because you took a schedule C writeoff in an earlier year.