I am using WHMCS version 4.2.1 for maintaining domain registration & website hosting services, in one of my websites. Currently, the automatic domain registration process is working great for both the existing & new clients. The main way to register domains automatically is to mark the respective invoices as paid, and automatically the domains get registered through my selected registrar.

Recently, I am facing a major problem in domain renewals, where the domain has been already registered by us in the past. The problem is that some of the corresponding invoices are not already generated for the domains & so I have to manually create invoice for each of those domain renewals.

However, I am unable to map that invoice with the corresponding domain. This is required because unless the domain knows that for its renewal, an invoice has been created, the marking of the invoice as paid will not instantiate the automatic renewal process through my registrar.

Can anybody please tell me the probable way of mapping the invoice with its corresponding domain?

I've tried to explain the problem as it is occurring in the best way possible. Still, if any more information regarding this is required, please ask.

Any help is greatly appreciated.