A blanket sales order represents a framework for a long-term agreement between you and your customer.
A blanket order is typically made when a customer has committed to purchasing large quantities that are to be delivered in several smaller shipments over a certain period of time. Often blanket orders cover only one item with predetermined delivery dates. The main reason for using a blanket order rather than a sales order is that quantities entered on a blanket order do not affect item availability and thus can be used as a worksheet for monitoring, forecasting, and planning purposes.
On the blanket order, each separate shipment can be set up as an order line, which can then be converted into a sales order at the time of shipping.
An example of when a Blanket Sales Order could be used is if a customer calls and places an order of 1000 units of an item and they want the items to be delivered in 250 units every week over the next month.