The limit custom field will allow the Administrator to set these fields per expense type and limit them to roles or link them to trips. If you wish, you can even link your own custom fields to certain projects, so that depending on the choice of the project only relevant fields will appear for the user.
Here are the steps to limit custom fields.
Go to Admin, select Custom fields.
Select the name of the Custom Field you would like to limit.
3. Click 'Limit the custom field to'
4. After selecting the limitations of your custom field in step 3, you can now click Save.