SAP ME21N

It creates a purchase order, the formal document ordering goods/services from a vendor, and is the central procurement transaction.

• Vendor and PO document type (header).
• Item lines: material/short text, quantity, plant, delivery date.
• Pricing conditions (net price, discounts, taxes).
• Account assignment (stock vs consumption: cost center/order).

The prerequisites for a purchase order are a shorter list than for a sales order and they fail in the same way, with a message naming the symptom rather than the cause.

• The vendor exists for that purchasing organisation. A vendor created centrally and not extended to the purchasing organisation cannot be ordered from.
• The material has a purchasing view for the plant. Basic data alone is not enough.
• The document type is configured with its number range and its permitted item categories.
• An account assignment category is available for what you are buying. Stock items post to inventory; anything consumed needs a cost object, and which cost object is legal is decided by that category.
• Pricing conditions or an info record if a price is expected to default rather than be typed.

The account assignment is where most first attempts stop. Buying a laptop for a department is a consumption purchase and needs a cost centre; buying raw material for stock needs neither, and the system will not let you supply one.

• Use the single-screen ME21N (not the older ME21).
• Reference a requisition or contract to speed entry.
• Check the release strategy status if approvals apply.

One habit worth forming: check the release strategy status on the header before telling anybody the order is placed. An order that is saved but not released has a document number and does not permit a goods receipt, which looks identical to a placed order from the outside and is not one.

Saving creates the order across a small set of tables.

• EKKO the header: order number, type, vendor, purchasing organisation, currency, and the release strategy fields.
• EKPO the items: material, quantity, plant, net price, item category.
• EKET the schedule lines: delivery dates and quantities.
• EKKN the account assignment, present only for items that have one.
• EKBE the history, which fills as goods receipts and invoices arrive against the order.

EKBE is the one worth knowing by name. Questions about what has been received and what has been invoiced against an order are answered there, and the purchase order history view in the transaction is a display of it.

• "Account assignment" errors, wrong/missing cost object for consumables.
• Material not maintained for the plant (missing purchasing view).
• PO blocked by release strategy until approved.

The rest of the set. ME22N changes an order and ME23N displays it. As with sales orders, display access is what most people asking to "see the PO" actually need.

The document sits in the middle of a chain: a requisition may precede it, a goods receipt and an invoice follow it, and the three way match between order, receipt and invoice is what accounts payable relies on. See VA01 for the selling side and MM01 for the material master.

Version note: the transaction is unchanged on S/4HANA and the tables above are unchanged, so purchasing is one of the areas where older material transfers almost completely. The Fiori applications for managing purchase orders are the strategic interface, and the business partner conversion means the vendor is now a business partner in a vendor role, which changes how the master record is maintained rather than how the order behaves.

• Treating a saved order as a placed order. An order awaiting release has a document number and permits no goods receipt. Check the release status before telling the vendor or the requester anything.
• Changing the price on a released order. Most release strategies reset on a value change, so the order silently returns to unreleased and the goods receipt fails a week later for a reason nobody connects to the edit.
• Entering a delivery date nobody agreed. MRP plans against that date and expediting chases against it, so an optimistic date quietly becomes a shortage somewhere.
• Using a free text item where a material exists. No material means no stock, no valuation and no purchasing history, and the shortcut is permanent for that order.
• Assuming account assignment is a formality. It decides whether the purchase becomes inventory or a cost, which is a finance decision being made by whoever is typing the order.