The list, in order
Disable the email and file account, then sign every session out, because a disabled account with a live session on a phone is still a live account. Change any password that person shared with somebody else. Remove their remote access. Take back or wipe the company phone and laptop. Cancel the building keys, the alarm code and the parking fob.
Then handle the arrivals. Set the mailbox to forward to their manager for a stated period, redirect anything that arrives through their name, and move any two-step login codes that go to their personal number onto an account the business controls. Keep the mailbox and the files intact for as long as your records policy says.
The accounts everybody forgets
The domain registrar, if it was set up with their address. Telecom and utility accounts opened in their name. Software subscriptions bought on a personal card and expensed. Trials signed up with the company card that renew quietly. The social media and advertising accounts, where a personal profile is often the only administrator. Scanner and printer setups that send to their mailbox. Anything with a licence key sitting in their inbox.
One more that costs businesses real money: a mail rule quietly forwarding company mail to a personal address, set up months before anybody resigned. Check the rules on the mailbox before you disable it.
Timing
Have the list ready before the last day and agree the hour with the manager. On a friendly departure, book a handover session while the account still works, because the things only that person knows are worth more than the equipment they are handing back.
Tell the team the account is closed and where the work now goes. Half the confusion after somebody leaves is people emailing an address that stopped being read.
When somebody leaves on bad terms
Disable at the moment of the conversation rather than at the end of the day. Preserve the mailbox and files before anything else, since deleting is the one step that cannot be undone. Check for forwarding rules and for large downloads or copies in the days before. Change every shared password within the hour. Tell the bank and your main suppliers who is authorised from now on.
Write down what was done and when. If the departure becomes a dispute, that record is what your lawyer will ask for first.
What makes it easy every time
Individual accounts for everybody, with no shared logins anywhere. Access matched to the job rather than inherited from whoever sat in the chair before. A joiners-and-leavers checklist that the office manager can run without calling anybody. Do that, and a departure becomes twenty minutes of routine rather than a week of wondering what is still open. It also helps on the day somebody joins, since the same list run backwards is how a new person gets everything they need before their first morning.