Backorder

A backorder is a customer order taken when stock is depleted, with delivery deferred until replenishment arrives. It is one of the two possible resolutions of a stockout — the other being lost sale. Backorder behavior dominates in categories where product substitution is hard (custom furniture, made-to-order spare parts, niche B2B materials), where the customer-supplier relationship is long-term and contract-based, and where the customer has already normalized waiting. In operations research, backorder is captured by a classical EOQ extension: the planned-shortage EOQ. Part of cycle quantity Q (specifically Q-S) is allowed to accumulate as backorders during the shortage interval, the remaining S is met from on-hand, and each unit-time of backorder is charged at penalty b. The optimal Q* expands by a factor of √((H+b)/b) under the square root. Backorder cost has two components: (1) the opportunity cost of the waiting time (erosion of customer-firm relationship, credibility loss), and (2) administrative overhead (notifying the customer, tracking the order, expediting if required). Two disciplines determine SMB backorder success: (a) the promised ETA must be realistic — a slipped commitment converts a backorder back into a lost sale, and (b) the backorder ledger must live in the ERP with explicit aging; orders older than 30 days should fire an automatic escalation rule.