To initiate a refund in the portal, follow these steps:
Go to Customers and press Contracts
Under Contracts search for the customer you wish to refund
Click on the right contract go to Bills and press on the bill you’d like to refund
Once you have clicked on the bill scroll down until and press Manage refund
You will get the following in the picture below. Write the amount (you don't need to account for VAT) and state the reason of the refund
7. Press "refund" and you are done!