Deactivating a user does not move what they own. The leads and opportunities stay with a person who cannot log in, and anything that routes to them keeps doing so.
1. Find what they still own
SELECT COUNT() FROM Lead WHERE IsConverted = false AND Owner.IsActive = false
SELECT COUNT() FROM Opportunity WHERE IsClosed = false AND Owner.IsActive = false2. Reassign it
Salesforce has a mass transfer tool for leads, and reports with a change owner action for records you have selected. For large volumes, use a data import tool to set the new owner. Decide first whether the leads go to a person, a queue, or back through the assignment rule, since the rule decides differently from a manual choice.
3. Stop new ones arriving
Search your assignment rule entries, flows, round robins and routing tool for the person. Each place that names them keeps routing to them. See round robins and inactive users.
4. Check the default owner and queues
If the departed rep was the default lead owner, or the only member of a queue, everything with no better match went to them. See leads going to the default owner.
5. Make it part of leaving
Add the reassignment to the process for someone leaving, with a named owner. Without it, the next departure repeats this.
Have it checked every night instead.
Routing Forensics connects as a read-only user and checks this, and the rest of your routing, against your real leads. Three design partners get a free health report on their own CRM, free for 90 days: what is leaking, where, and what it is worth. Apply for a place.
The free scan cannot see this one: it reads assignment rules, flows and queues only. Connected, it is checked every night.