What exchange rate is used to convert transactions?

If you do not have sufficient funds on your foreign currency account when paying abroad, the SELL exchange rate will be used for conversion on the CZK account and BUY exchange rate on the foreign currency account.

If you do not have sufficient funds in your CZK account and you use funds from your foreign currency account, then the BUY exchange rate will be used for conversion on the CZK account and the SELL exchange rate on the foreign currency account.