An excess or advance payment is accounted as credits for the customer. Here's a way to record those advance payments.

• Go to the Customers tab
• Click the customer for whom you need to add the advance payment.
• Click the Invoice Payment link, on the right hand side of the page
• Go on to enter the payment information like the date and amount received
• Click the Save button
• Now the system would ask if you want to save the payment as credits to the customer. Please agree to that

The credits will be added to the customer. When you invoice or add a payment, the system would remind you about these credits. You may use them for the future invoices at any time.