Adding an expense type to a per diem overage group You can add an expense type to a per diem overage group: Create or modify a per diem overage. See Adding a per diem overage. Click Add in the expense type section. Specify this information: Expense Type The expense type to map to this overage group. Special Type The type of expense is a tax type. Locale The locale for this expense type if the overage is modified. Tax Account The name of the tax account if you are modifying an overage. For example, Room Tax Overage. Click OK to save the data.