A refund in Zoho CRM

A refund in Zoho CRM

Hello!

If i have a refund of products, how can i do it in zoho crm?

For example, i made an invoice with 4 products with price 2 euro each of them.

Some days later, the customer returns them (for a reason), then i have to update the qty kai to give the money back.
How can I do this?