If you sold the currency in 2017, you may report it. Until it is sold, it is not considered a loss.
- List each trade/sale in the Stocks, Mutual funds, Bonds, Other interview
- When asked Did you get a 1099-B or a brokerage statement for these sales? select No
- Type of investment you sold select "Everything else for held for investment"
Be sure to translate proceeds of each sale into US dollars at the time of the sale or movement