purchase order (PO)

A purchase order (PO) is a formal commercial document issued by a buying organization to a supplier that specifies the items, quantities, prices, and terms under which goods or services are to be provided. In industrial and manufacturing environments, the PO is the primary authorization for a supplier to deliver materials, components, tooling, services, or subcontracted operations.

Key characteristics

In regulated manufacturing and supply chain operations, a purchase order commonly includes:

• Buyer and supplier identification and addresses
• PO number and issue date
• Line items with part numbers, descriptions, and revisions
• Quantities, unit prices, and total value
• Requested or required delivery dates and ship-to locations
• Terms and conditions (payment, Incoterms, liabilities, etc.)
• Quality and regulatory requirements (e.g., certificates, FAI/AS9102 note, special processes)
• Reference to specifications, drawings, or work instructions

The PO is typically created and managed in an ERP or procurement system and is often integrated with MRP, inventory, accounts payable, and supplier collaboration tools.

Operational role in manufacturing

Operationally, the purchase order:

• Links demand to supply by tying MRP or planning requirements to specific external supplies
• Provides the primary structure for tracking supplier commitments, delivery status, and backlog
• Serves as the reference for receipts, inspections, and NCRs at incoming inspection
• Feeds financial processes such as accruals, three-way match (PO, receipt, invoice), and costing
• Often links to internal work orders or projects to maintain traceability of purchased content into finished goods

In many aerospace and regulated environments, detailed line-level PO data (part, revision, lot, required certs) is used to maintain traceability and to verify that supplier deliveries meet contractual and regulatory requirements.

PO in backlog and risk visibility

For supply chain and capacity management, purchase orders provide the structure against which suppliers communicate confirmations, updated delivery dates, capacity constraints, and change notifications. Backlog execution risk and material shortage risk are typically assessed by comparing supplier-confirmed PO data to internal demand dates, work orders, and program schedules.

What a purchase order is not

• It is not an invoice. The supplier invoice is a billing document raised after shipment or service, often matched back to the PO.
• It is not a contract in the broader legal sense, although it usually incorporates or references contractual terms.
• It is not a work order. Internal work orders govern in-plant manufacturing steps, whereas POs govern external procurement and services.

Common confusion

• PO vs. purchase requisition (PR): A purchase requisition is an internal request to buy; the purchase order is the external document sent to the supplier.
• PO vs. schedule agreement/release: Some organizations use long-term agreements with periodic releases instead of discrete POs for each order; the release still functions similarly to a PO line operationally.