There are 2 stages to discharging a customer from active services:
ON HOLD: Select to Put Services on Hold in the Service User screen
DISABLE: After services have been put on hold, you can select Disable
Setting them as On Hold just means there is a long period expected of not providing them services. You can set them back whenever you are starting services again.
Disabled status means you do not expect to deliver any services to them in the future.
Both actions can be undone later if you need to revive them again.
When they are on hold or disabled then these service users will not show up in the normal dropdown lists etc until they have been updated back to Active status.