How do I record a refund for the advance payment I received from a customer?
To record a refund for the advance payments received from a customer:
- Go to the Sales tab on the left sidebar and select Customers. 
- Select the customer for whom you want to record a refund. 
- On the customer details page, click the Unused Credits. A pop-up will appear with the list of unused credits.  
- Click Excess Payment, and you will be taken to its payment receipt.  
- Click the More icon and select Refund.  
- Verify the details, enter a reference number and a description, if required, and click Save. 
The refund for the advance payment made by your customer will be recorded.