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To switch between these calculation mode, you can use the Calculate Exchange Rate Differences on Month Closing Only option on the Administration > Settings > Money form.
Month-End Calculation
Month-end calculation of exchange rate differences is performed in both calculation modes.
To include the calculation of exchange rate differences in the month-end closing process, you need to select the Calculate Exchange Rate Differences option on the Accounting > Service Tools > Month-End Closing form. You can review the results of the calculation and corresponding journal entries in the generated Month-End Closing document when you click the 
button. For more information on month closing, refer to Month-End Closing Service Tool.
During month-end closing process, balances of following accounts (if they are maintained in other currencies than the accounting currency) are revalued by using the current (month-end date) exchange rates:
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Gain or loss resulted from exchange rate fluctuations for a document is calculated as follows:
1. The document amount is revalued based on the exchange rate of the foreign currency with respect to the accounting currency on the date of month end.
2. Gain or loss is determined as the difference between the document amount in the accounting currency on the month-end date and the document amount on the last revaluation date that can be the transaction date if the document was posted during the current month or the previous month-end closing date if the document was posted earlier. If the difference is greater than 0, the gain is recorded; otherwise, the loss is recorded
Exchange differences for for transactions that were paid for during the period are also calculated on during the month-end closing, using the exchange rate on the date of payment.
Calculation during the current period
If the Calculate Exchange Rate Differences on Month Closing Only option is not selected on the Administration > Settings > Money form, the exchange rate differences are calculated additionally during the period as follows:
- For each new foreign currency transaction, the amounts are also recorded in the accounting currency by using the exchange rate effective on the transaction date. If this calculation is initiated for instance by an Invoice or Invoice Received, no exchange differences are calculated for the particular document. However, simultaneously, all the foreign currency transactions associated with the related contract, balances of GL accounts (involved in the transaction) are revalued based on the actual rate, and this date becomes the last foreign currency revaluation date for the transactions that were adjusted.
- If the calculation is initiated by an outgoing or incoming payment, for instance Cash Receipt or Cash Payment, the amounts of exchange differences are calculated for the particular document if the exchange rate on the date of payment differs from the rate on the date of original transaction (sales or purchase). Again, simultaneously, all the foreign currency transactions associated with the related contract, balances of GL accounts (involved in the transaction) are revalued based on this rate, and this date becomes the last foreign currency revaluation date for the transactions that are adjusted.
Default GL Accounts
If the total amount of gain or loss (incurred due to exchange rate differences) is in the interval (-0.005, +0.005) no gain or loss is registered.
If the resulting sum is equal or greater than 0.005, the sum is posted to the default account selected in the Gains on Exchange Differences column on the Accounting > See Also > GL Accounts by Default form. You can use the same default "Gain" account for all entities, or you can select separate accounts for entities.
If the resulting sum is equal or less than -0.005, the sum is posted to the default account selected in the Losses on Exchange Differences column on the Accounting > See Also > GL Accounts by Default form. You can use the same default "Loss" account for all entities, or you can select separate accounts for entities.