There are several ways to use credit memos:

If a selected customer has open credit memos, you’ll find them underneath the “Total” section when creating a new invoice, or editing an open invoice to that customer.

To apply a credit memo on an existing invoice, select match payment in the Invoices list.

If the customer has open credit memos, the match payment screen will show the credit memos and auto apply them as a payment. You can choose to not apply the credit memos by unchecking them.

Applied credit memos can be found in the Credit Memos page, under the “Applied” tab.

Additionally, invoices with applied credit memos will show credit memos as part of the payments matched to them.

After applying the credit memo, if the invoice has an outstanding balance, you can choose to download a new PDF version of the invoice or resend the invoice to your customer.