The rates returned from the Official exchange rate APIs (GetOfficialRate(s), GetOfficialHistoricalRate(s)) are typically determined by the central banks or equivalent authority within each country.

Official rates are not typically quoted in the same terms of Bid/Ask/Mid as the general forex rates available in our services. Instead, the central banks tend to calculate a static rate on a specific date, and only quote this rate for a limited list of currencies. Central banks may not provide "reverse rates" for each other's currency.

For example, the Polish National Bank quotes an exchange rate for their Zlotyc (PLN) to Chinese Yuan (CNY). However, this does not imply that there will be an official rate of CNY to PLN; it will depend on whether the Chinese Central Bank PBOC publishes a rate specific for their Yuan to the Polish Zlotyc.

Please refer to the following link for a list of Central Bank coverage for each service version, and the currency exchange rates they publish: https://www.xignite.com/product/forex#/DeveloperResources/request/ListOfficialRates