In WHMCS, you can configure domain reminder settings to automatically notify your clients about upcoming domain renewals. This helps ensure that they have ample time to renew their domains and prevent any disruptions in services.

Here's how you can set up domain reminder settings in WHMCS:

1. Log into WHMCS: Access your WHMCS admin panel using your username and password.

2. Navigate to Configuration: Click on the "Configuration" tab in the top navigation menu.

3. Automation Settings: Under the "System Settings" section, click on "Automation Settings."

4. Domain Renewal Notices: Scroll down to find the section labeled "Domain Renewal Notices."

5. Enable Domain Renewal Notices: Check the box to enable domain renewal notices.

6. Set Days Before Expiry: Enter the number of days before a domain's expiry date that you want WHMCS to start sending renewal notices to your clients.

   For example, if you set this to 30 days, WHMCS will start sending notifications one month before the domain's expiry date.

7. Configure Additional Options (Optional): Depending on your preferences, you may find other options related to domain renewals that you can configure, such as "Use Legacy Domain Management" or "Send Renewal Notices for Addons".

8. Save Changes: After configuring the domain renewal notice settings, click the "Save Changes" button to apply your modifications.

9. Customize Email Templates (Optional): You can customize the email templates for domain renewal notices by going to "Configuration" > "System Settings" > "Emails." Look for the relevant template named something like "Domain Renewal Notice".

   Customize the subject and message of the email to suit your business style and preferences.

10. Test the Notifications: Before relying on the automated system, it's a good idea to perform a test run to ensure that domain renewal notices are being sent as expected.

By enabling domain renewal notices in WHMCS, you can help ensure that your clients are aware of upcoming domain expirations and can take the necessary steps to renew their domains in a timely manner.