This article explains the time off request notifications and time off approval.
When a user submits a time off request (see Enter a time off request), approvers are sent notifications of the request. Who receives a notification to approve the time off depends on your organization's OnePlan configuration.
If the environment has "Resource Managers" enabled, OnePlan will send the time off request notifications and emails only to the requesting user's resource manager mapped in the OnePlan configuration. See How do I set Resource Managers?.
If the environment only has the "Manager" field configured in the Resource Center, all of the group Owners and the requesting user's "Manager" will receive the time off request notifications and emails.
If the environment does not have "Resource Managers" or the "Manager" field configured, all Owners and Managers in the OnePlan group will receive time off request notifications and emails. Team members, Executives and Contributors will not receive notifications or emails.