Support and response times
When somebody leaves, how fast is their access actually gone?
Offboarding is the part of the process most businesses handle badly, and it is usually not a technical failure. It is that nobody told IT for a week.
When you tell us, we disable the account, revoke active sessions and tokens rather than only changing the password, remove access to cloud services, wipe or remove company data from any enrolled mobile device, deal with the mailbox according to what you need retained, and free the license so you are not paying for someone who left in March. That is minutes of work, not a project.
For a planned departure, tell us the date and time in advance and we schedule it to the minute so access ends exactly when employment does. For a difficult departure, tell us before the conversation happens rather than after, and we will be ready to act while it is taking place.
Build the habit of telling us as part of the same routine that handles their final paycheck. The accounts we find still active at takeover belong to people who left years ago, and every one of them started with a good process that nobody triggered.