What is the difference between supply order management and order-to-cash?

Order-to-cash (O2C) covers the sales side: from receiving a customer order to invoicing and payment collection. Supply order management sits on the buy side: it manages purchase orders sent to suppliers to replenish inventory and fulfill demand. While both involve order workflows, they serve opposite ends of the Supply Chain. Companies need both to run smoothly, but the planning intelligence required on the supply side — connecting orders to forecasts, safety stocks, and supplier constraints — is fundamentally different from O2C process optimization.