How do you allocate a net refund (via worldpay) against two different customer accounts - ie one is a credit note and one is an invoice

I'm happy to share the solution to this concern, @accounts11_2. There are a few things to perform to record this net refund in QuickBooks Online. Let me jump in and explain this further to you.

We can record an invoice for your first customer and enter the original amount.

Here is how to create an invoice:

1. Select + New.
2. Pick the Invoice.
3. Enter the customer name and the date from the net refund sync from Worldpay. 
4. Enter products and services and the original amount of the transaction.
5. Once done, Save and Close.

On the other hand, create a credit note from another customer.

1. Select + New.
2. Choose the Credit note.
3. From the Customer dropdown, select the customer's name.
4. Enter the credit note details, such as the date and the amount. 
5. After that, Save and Close.

Next, apply the credit note to the created invoice.

1. Tap + New.
2. Select Receive payment.
3. From the Customer dropdown, select the customer.
4. From the Outstanding Transactions section, choose the open an invoice to match them
5. From the Credits section, select the credit notes you want to apply.
6. Lastly, click Save and Close.

Moreover, you can refer to this article for your additional guide: Create and apply credit notes or delayed credits in QuickBooks Online.

Plus, to avoid discrepancies, I recommend deleting the net refund transaction if the amount is synced in QuickBooks Online.

Keep me posted if you have other queries about your banking transactions. Have a great day ahead.