Hello @mccullochlandsca,
As of the moment, there isn't an integrated setting to switch the default currency of an account. With this, you'll have to cancel your account with the UK Pound currency and start one with the correct currency accordingly.
That said, the following articles below will guide you through the steps if you wish to proceed the workaround mentioned:
Also, I've got you this reference helpful for guidance while working with us: QuickBooks Self-Employed Overview.
If you have any other questions, please let me know in the comments below. I'll be here to lend a hand.
