Could you provide some more details, such as which API service or report you are using?
Note that every account has a single currency associated with it, which you can get from the
Customer,currencyCode attribute resulting from a
CustomerService.get call. All monetary values returned in reports and other API calls will be in the account's currency. If an account's currency is GBP and you need values in Euros, you will have to perform the conversion within your application.