As of my last knowledge update in September 2021, WHMCS does not have a built-in feature to automatically delete inactive clients. However, you can achieve this through custom scripting or by using third-party modules or extensions.

If you're considering implementing this feature, it's important to approach it with caution. Deleting client accounts can have significant implications, especially in terms of data privacy and legal compliance. Always ensure that you have proper consent and consider the implications of deleting client data.

If you have specific requirements for automatically deleting inactive clients, I recommend consulting with a developer or WHMCS expert who can assist you in implementing a custom solution tailored to your needs. They can help you create a script that periodically checks for inactive clients and removes them based on your defined criteria.

Remember to always have proper backup and recovery procedures in place, especially when implementing automated processes that involve data deletion.