The 846 tells a trading partner how much of each item is available, and where. A typical advice lists items by part number or GTIN with quantity on hand or available to promise, and sometimes quantities on order with expected dates, by warehouse or location. It is usually sent on a schedule, often daily, or whenever stock changes significantly.
The 846 isn’t triggered by a single order; it runs alongside the order flow and shapes it. Suppliers send it to retailers and distributors so they can show stock online and plan purchase orders (EDI 850). In drop-ship programs it decides whether a retailer can sell an item at all. Retailers may also send store or warehouse inventory to suppliers who manage replenishment for them.
Stale or inaccurate 846s are expensive. If the feed shows stock that isn’t there, orders get placed that can’t be filled, leading to cancellations, backorders and poor OTIF results. If it shows too little, sales are lost. Common causes are infrequent updates, quantities that ignore open orders, and item identifiers that don’t match the buyer’s catalog.