Credit note related to a pre-implementation dated invoice

Credit note related to a pre-implementation dated invoice

I have a customer returning goods for a pre-implementation dated invoice, thus the invoice does not exist in Zoho.
Previously, I have entered Opening Balances for Customers and Inventory.

A Credit Note in Zoho books cannot be issued without selecting an invoice.

How can I achieve the following:
  1. Increase stock by the number of items being returned.
  2. Decrease the balance of the customer who returned the goods.