A currency exchange rate is a dated record telling Business Central how to convert a foreign currency amount into local currency when a document is posted.
A currency exchange rate in Business Central is a record attached to a currency code with a starting date, an exchange rate amount and a relational exchange rate amount. Together these two amounts express the conversion, for example how many units of local currency correspond to a given number of units of the foreign currency. When a document is posted, the system applies the most recent rate whose starting date is on or before the posting date of the document, and a separate adjustment rate can be held for period end revaluation.
Press Alt+Q and search for Currencies to open the currency list, then open the exchange rates for the currency you need. Searching directly for Currency Exchange Rates leads to the same data. The local currency code and the general rounding rules sit in General Ledger Setup, while the realised and unrealised exchange rate gain and loss accounts, together with the rounding precision of that currency, are held on the currency card itself.
Local currency is CHF and you post a purchase invoice from a German vendor for EUR 12,000 on 15 March 2026. With a rate record starting 1 March 2026 where an exchange rate amount of 1 corresponds to a relational amount of 0.95, the invoice hits the general ledger as CHF 11,400 while the vendor ledger entry keeps its EUR 12,000 remaining amount. If the payment goes out in April at 0.97, the difference of CHF 240 is recognised as a realised exchange rate gain or loss.
The classic error is entering the two amounts the wrong way round, which multiplies where it should divide and produces figures that are off by a large factor. Missing rates are more insidious: if no record exists for the new month, Business Central keeps applying the last known rate without warning, so amounts drift quietly. It also surprises people that editing a rate after the fact does not restate posted documents; only the exchange rate adjustment routine revalues open entries.
If you post in foreign currency regularly, load rates on a fixed schedule instead of when someone notices they are missing, and run the exchange rate adjustment before closing a period so open vendor and customer balances are revalued consistently. Where an external rate service is available, a recurring background job avoids the gaps that manual entry leaves behind.
The most recent exchange rate whose starting date is on or before the posting date of that invoice. The currency factor is taken from the posting date, not the document date, which matters on purchase invoices where the two differ. A rate entered later with an earlier starting date does not change documents already posted.
Because open entries in foreign currency keep their original local currency value until the exchange rate adjustment runs and posts the unrealised difference.
Zentriq's AI tools automate many of the manual processes around currency exchange rate in Business Central. Learn about the Zentriq Agent or try Zentriq PunchOut to see how AI simplifies procurement in BC.