You need to create the credit from the invoice you took the payment on and then that money will be in your credit balance for the project and you can apply it to any other invoices in the project.
Watch this video on credits and retainers:
Use your credit balance for other invoices in the project
You need to create the credit from the invoice you took the payment on and then that money will be in your credit balance for the project and you can apply it to any other invoices in the project.
Watch this video on credits and retainers: