In the Invoice Items card click the add button; a new row appears where you type a Name ("Type to add a service"), a Quantity, choose a Unit (None, Items, Hours, Days, Weeks, Months) and an Amount (price per unit). The row total is quantity × amount. Rows without a name are discarded on save. Each row has a Hide on Customer BEO toggle. Invoice Items are the right place for room rental, delivery surcharges, service charges, gratuity you want to bill up-front, or any one-off fee; they are summed as Invoice Items in the Totals card and are the only billable lines (with Labor & Equipment) on an Invoicing-type proposal. Requires the Custom Charge module.