Hello @snapperjonno
If the refund is of an overpayment, there isn’t a way to tag it from the bank side of things, only from the other side (which in turn creates a tagged bank entry).
Firstly, go to the client record (Sales >> View all Clients), and click View >> All Payments.
Then, find the overpayment. This would be shown with the text “£x.xx remains unallocated” next to it> or, if you have a lot of payments, you can do an advanced search to find just the ones that have unallocated balances:
View the payment, and then click Refund Balance at the top. Hopefully the amount is the same as the transaction you already have in the bank account.
Confirming this will create a new tagged bank transaction, so as a result you should have 2 transactions for the same value, on the same date, but one untagged. At this point, you can safely delete the untagged entry to rebalance your account.
I hope that helps?