How do I determine which year to file a casualty loss in?

[DanielV01 · Accepted solution]

It depends.  I am answering this question under the presumption that this refers to the special disaster relief provisions that are in place for the victims of Harvey, Irma, Maria and the California fires.  Normally, a casualty loss must be claimed in the year it occurs.  However, with these special provisions, you may file the loss for the year either for 2017 (the year of the disaster) or for 2016.  Which year should you use?  The simplest answer is:  the year you get the better result on your tax return for a larger refund.  Generally speaking, this will be the year that you had more income (although there are other factors as well).

The only true way to be able to know for sure is to first prepare the 2017 return without the casualty loss, and then add the loss in order to compare the difference in the refund; and then do an amended return of your 2016 return to include the disaster relief provision.  Here is some information on how to prepare last year's amended return:  https://ttlc.intuit.com/replies/5114064