If there’s no VAT, then you can simply tag “Money In” transactions as “Something else not on the list”, and tag them to 4000 General Sales, if you wish.
What some people find easier, is to raise a daily or weekly invoice. This would also allow you to assign them to specific clients if you wish.
There would no need to worry about the invoices if you wish, as they’re logged elsewhere. It would just be a case of making sure they are accurate. If you’re using QuickFile for tax returns etc., then you would need to ensure they tally up with the rest of your invoices too for accurate figures.
You can set the GBP/USD equivalent for certain things within QuickFile (for example, if a USD invoice is paid for in GBP), which would calculate the effect exchange rate for you.
You may find these articles helpful: