How to allocate a single credit across several sales invoices to clear balances created by auto-deduction of charges by bank from customer payments sales invoices

Hello Info284, 

Welcome to the Community page, 

As long as the invoices are for the same customer then yes one credit note for a total amount can be posted and used to pay off. You just need to go into the customer select the invoice, click on receive payment make sure the credit note is ticked and also any of the invoices that relate to that credit then click save and close.