Any non-GBP account will need to be adjusted due to currency fluctuations. So although the bank account has a balance in it’s currency (e.g. USD), in the background and on reports like your Chart of Accounts and Balance Sheet, there’s a GBP balance.
On the bank account itself, you can go to Options and record the currency gain/loss there. The values here only affect the GBP balance.
As an example, let’s say the balance of your USD account is $100.00, and the GBP value currently on QuickFile is £80.00. But as of today, the value is £75.00, so it needs to be adjusted down £5.00. I’ve kept the numbers simple for the purpose of this example.
To do this, I’d go to record a currency gain/loss, and enter the following journal entry:
This then adjusts your chart of accounts to the new value, and the bank account balance remains unaffected.
Hope that helps!