Currency codes used in FIX are those defined in ISO 4217 standard. To obtain the current valid list please contact the ISO 4217 secretariat at +44-181-996-9000.
At the time of writing the list of valid currency codes could be found on Web:
Note: Prices defined in FIX messages should be made consistent with the currency code used. In some markets, prices are quoted as multiples or fractions of the currency, FIX messages should normalize the amount to coincide with the indicated code (e.g. UK securities are quoted in pence but must be represented in FIX messages as pounds).