Cumulative Lead Time is the total accumulated time for an end item to be available for sale. This will include the time to source and purchase all raw materials needed for the manufacture of the item. This includes time for purchase order approval, time for supplier to supply, time for delivery to our warehouse and time for receiving and inspection. In also includes time for the manufacture of the end item though all levels of the bill of material. The cumulative lead time is calculated to include all time until the item is available for sale, so this will also include the time taken to receive the finished product from production unto the FG warehouse.