Expense categories are defined in Settings>Categories. They are linked to the Budgets feature. These categories aim to help you track the nature of costs.
Admins can add, edit or delete values.
Add a value : click on "Add a category"
Edit a value : click on the pen tool
Delete a value : click on the bin icon
If there is at least one value in the expense category, the field appears in all requests.
By default, the field is mandatory to fill for Requesters but of course it's possible to make it optional (you can ask Support teams or your account manager).
Expense categories and export
Expense categories are exported when you export a spending marked as ready, from the export tab, or in the export that you can download from All Payables page.
Edit an expense category on a payment
To change the expense category assigned to a payment, I can go to Bookkeep > All payments > my payment > Spend category.