eBillingHub can normally handle two types of adjustments or discounts, but this depends upon the functionality available in your Time & Billing system and your client's format.
Invoice Level Adjustment. The electronic billing file is created with a line item designated by an E999 code for expenses or an L999 cost for tasks. The amount of this line item is a discount which applies to the entire invoice. For example, in the LEDES format, the EXP/FEE/INV_ADJ_TYPE will be IE for expenses or IF for fees. The client template determines how many adjustment lines are displayed.
Line Item Adjustment. If line item adjustments are supported, the line item adjustment will be entered in the designated adjustment fields on the line item. For the LEDES format, this is the LINE_ITEM_ADJUSTMENT_AMOUNT field.