Available to promise (ATP) is the quantity of a product you can commit to a new customer order and still deliver on time. It is calculated from current on-hand inventory plus scheduled incoming supply (purchase orders or production runs), minus the quantities already promised to other orders. In short, ATP answers a single question a buyer keeps asking: “How many can you actually ship me, and by when?”
How it works
A basic ATP figure starts with on-hand stock, adds confirmed inbound supply with known arrival dates, then subtracts every unit already committed to open orders, draft orders, or reservations. Because incoming supply has dates attached, ATP is often time-phased: the amount you can promise for next week differs from what you can promise in a month once a purchase order lands. Backorders and safety stock reduce what is truly promisable.
Why it matters
Selling stock you cannot deliver is one of the fastest ways to lose a B2B account. ATP gives sales a defensible number so quoted lead times hold up. It separates “we have 400 in the warehouse” from “we can promise you 250 by the 14th,” which is the figure that actually matters on a purchase order.
ATP in B2B quoting on Shopify
Shopify tracks committed and available inventory per location, but standard quotes rarely check it. When a wholesale buyer requests 500 units, the person building the quote should confirm ATP before stating a ship date, factoring in other open quotes and draft orders that already reserve stock. Turning a request into a draft order surfaces the commitment early, so two large quotes do not silently promise the same pallet.
Example
You hold 300 units, a purchase order for 200 arrives on the 20th, and 150 are already committed. ATP today is 150 units. After the 20th, ATP rises to 350, so a quote for 400 should promise 150 now and the balance after restock.