There are two types of credits that are normally issued: full credit and partial credit.
For full credit, follow below:
1. Go to the selling invoice that you need to issue credit for.
2. Go to the "orders" tab.
3. On the right upper side of the screen, you will have a "credit" button:
4. Once you click the credit button, the system will generate a credit invoice and all orders will showing in negative amount:
5. The credit invoice will be created in status "finance approved" and will have a number auto generated. It will also show in the reference field the number of the selling invoice that was credited.
To issue partial credit:
1. Go to the economics tab > selling
2. Mark the orders you wish to credit and click on credit invoice
** It is also possible to issue credit through the SO.