You can't delete a client, only deactivate.  That merely hides that particular client from your dashboard and does nothing else.

The reason is that Intuit Link is, in reality, a common portal between your account and your clients.  Your invitation for the relevant tax year allows both you and your client to access the portal to communicate and share documents.  Your client's account with Intuit (and Intuit Link as an extension of that) will continue to exist.

See this post for how you can deactivate a client in Intuit Link: https://proconnect.intuit.com/community/lacerte-tax-discussions/discussion/intuit-link-client-deacti...