How can I enable users to approve purchases on the budget holder's behalf?
This article details how to give users the ability to approve purchases on behalf of others.
Approving expenditure on others behalf
ExpensePlus allows users with the appropriate User Role permissions to approve purchases on behalf of others. Therefore, if a budget holder (Primary approver) is away on holiday or sick leave, others can cover their approval responsibilities.
This permission is set on the Manage User Roles screen.

When a Purchase is submitted but not approved the same day, ExpensePlus will send out a daily notification at 7am to the Primary approver until the outstanding purchases have been approved.
Top tip: If a Primary approver is due to be away for a prolonged period of time, and it is not possible to cover their approval responsibilities on a daily basis, it may be worth temporarily updating the expenditure categories to replace the primary approver.
To help you better understand the Approvals module as a whole, please visit the module overview page here.