As soon as a user is deactivated in Salesforce, changes to records owned by the users are prevented.
You generally want to deactivate a user once all the T+E Items are processed (invoiced).
Alternatively, you can assign the ownership of the T+E Items to another (active) user.
Steps: go to > Setup > Users ... and select the user and click on the Create/Update Resource link.
(you may have to add the Custom Link "Create/Update Resource" to the User Layout)
In section (1) you would create the Resource, add License and Permission Set
Changing Record Ownership
In section (2) you manage owned (transaction) data - mainly TE Items and Reports.
In the User owned T+E Items section you can view
- status and number of not approved hours
- status and number of not invoiced hours
In the example, there are quite a few completed hours, but only 18 of them are marked as billable and not invoiced.
You could now submit and approve the hours as well as create an invoice for them now (before deactivating the user) - or change the ownership of the records to another active user:
- Not Invoiced: all T+E Items which are marked as billable, but not invoiced yet
- Not Approved: all T+E Items wuth the status of New, Completed, Not Approved or Submitted
Changing the ownership of the T+E Items has no impact on reporting, as you usually report on the Resource - not the owner.
Owned Reference Records
In section (3) you can change the ownership of Reference Records (e.g., Resources, Projects). When a de-activated user owns a referenced record like a Project, any updates of the project will fail. So you need to change the owner of referenced records.
After clicking on "Refresh Transfer Options", the main reference objects are displayed with the number of records owned by the user. Select a new (active) user and click on Transfer Ownership.