Odoo14 is about to launch and it will came up with new exiting feature to reduce lot of rework or mistakes.
Switch to Refund/Credit note is one the good feature of Odoo14 will release with Odoo14.
While entering the data uses can make mistakes i.e. Instead of entering refund user created Invoice / Bills entry. In older version of Odoo you need to cancel the invoice and go to the refund and create the refund.
Odoo14 made it easy for users. Just one click and you can change you normal invoice / Bill to refund or credit note. Goto Action and choose "Switch into Refund or credit note."