Enable expense report email notification

Enable email notifications so that approvers receive an email when an employee submits an expense report. Employees also receive email notifications when their expense report is approved, partially approved, partially declined, or declined.

Subscription	Time and Expenses
Regional availability	All regions
User type	Business user with admin privileges
Permissions	Administration Application subscriptions: List, View, Configure

Go to Expenses > Setup > Configuration.
Find the Expense report approval settings section.
Select Enable expense report approval.
Select the Email notification checkbox.
Select Save.