In the Business Central UI, it is possible for the user to override the currency exchange rate used for sales or purchase invoices/credits.
However, the REST API does not seem to allow the currency exchange rate to be submitted for a new sales or purchase invoice/credit. The REST API does accept the foreign currency amounts and a currency code, but specifically does not accept an exchange rate.
Please add a feature to allow an external application to create new foreign currency sales or purchase invoices/credits whilst also supplying the currency exchange rate for an invoice/credit in the payload. This is required to avoid potential differences of base currency amounts between an external application and Business Central.
Many thanks for your attention.