Controlling Client Domain Renewal Orders
The ability for clients to place domain renewal orders from the client area can be switched on and off. When disabled, customers will need to pay the auto-renew invoice to renew their domain.
In WHMCS 8.2 and later, you cannot renew a free domain in the Client Area unless it is bundled with a product or service.
Navigate to Configuration > System Settings > General Settings > Domains (Setup > General Settings > Domains in WHMCS 7.10 and earlier).
Check or uncheck Enable Renewal Orders as desired.
Click Save Changes.
Client Area Display
The Client Area, with renewal orders disabled:

The Client Area, with renewal orders enabled:
