An overpayment occurs when a customer provides payment for more than the total remaining balance of an invoice. Even though it may seem infrequent, it can happen quite often due to automatic payments, subscriptions, product price changes. WHMCS creates a credit balance adjustment but it doesn't bill the overpayment at all. This may result in tax evasion since you are not invoicing these amounts properly. Here is how Billing Extension handles the issue.
- Proforma #1200
- Total Due: 100 EUR
- Total Paid: 150 EUR
- Overpayment: 50 EUR
First of all the Proforma #1200 is converted into invoice and WHMCS adds the 50 EUR overpayment to client's balance. Right after, the module updates the resulting invoice so that it shows a new line like it follows:
Now let's suppose that client makes a further overpayment on the same invoice. All subsequent overpayments are handled as new and separate invoices so that the date of the original invoice doesn't change. For more details refer to this article.