This section of the foreign currency invoicing KB article explains how to journal out currency fluctuations in non-GBP bank accounts. The underlying GBP nominal balance on a foreign currency account in QuickFile will naturally drift over time away from the true value per the exchange rate on a given date, because when you do a cross-currency payment or transfer it only adjusts the underlying GBP balance on the currency account by the same GBP amount as the other side of the transaction (i.e. it uses the exchange rate you specified for the payment rather than the true exchange rate for that day). The loss/gain journal lets you re-value the foreign currency account at the current exchange rate and put the balancing entry to currency charges, so you should do this at least once on your year end date and possibly more frequently at other points through the year.