Available to Promise

Definition

Available to Promise is the quantity of product that can be committed to a new customer order, based on current inventory, scheduled receipts, and existing demand already reserved for the same time horizon.

What is Available to Promise?

Available to Promise, commonly shortened to ATP, is an order promising calculation used in supply chain planning and customer order management. Its purpose is to tell the business what quantity remains truly free to commit after other obligations have been considered. It is therefore a commitment measure, not just a stock count.

In practice, ATP pulls together inventory on hand, planned receipts such as purchase orders or production orders, and the demand that has already been accepted. The result helps customer service, sales, planning, and operations answer two linked questions: can the order be accepted, and if so, when can it be delivered reliably.

In procurement and supply chain operations, ATP is closely tied to inbound reliability. If supplier schedules are wrong or replenishment plans slip, ATP may overstate what the company can really promise and create avoidable service failures.

How to Calculate Available to Promise

A simplified ATP calculation starts with supply available in the period and subtracts customer demand already committed in that period. In a basic make to stock example, ATP for the first period may be calculated as on hand inventory plus scheduled receipts minus booked customer orders up to the next replenishment point.

For later periods, ATP is often calculated as the scheduled receipt in the period minus existing orders due before the next receipt. Some systems calculate ATP discretely by period, while others use cumulative logic across multiple future buckets. The exact method depends on the planning model and order promising rules.

Available to Promise vs Inventory on Hand

Inventory on hand shows what appears physically available in stock. Available to Promise shows what remains commercially available after allocations, existing commitments, and scheduled supply are considered. The numbers can differ substantially because stock may already be reserved or because incoming supply changes what can be committed later.

This is why ATP is a much better indicator for order acceptance than inventory alone. A warehouse may hold stock, but that stock may not be free to promise.

Available to Promise in Procurement and Planning

Procurement affects ATP indirectly but materially. Supplier lead time, purchase order reliability, delivery date changes, and inbound capacity constraints all affect the quality of future receipts in the ATP calculation. If procurement data is weak, ATP becomes less trustworthy and customer commitments become more fragile.

For organizations dependent on imported goods, long lead times, or volatile supply, ATP quality is often a reflection of how well procurement, planning, and order management are connected.

Benefits of Available to Promise

ATP improves order promising by basing commitments on actual supply position rather than sales optimism or simple stock visibility. It reduces overcommitment risk, improves customer communication, and supports smarter allocation when supply is constrained.

It also gives the business a shared supply language. Sales, service, planning, and procurement can work from the same available quantity logic rather than competing interpretations of what is in stock.

Limitations of Available to Promise

ATP is only as accurate as the data behind it. If inventory accuracy is poor, reservations are late, purchase orders are unreliable, or production schedules are not updated, ATP can become misleading. That creates a false sense of certainty rather than a useful commitment tool.

It can also be difficult to manage in environments with heavy manual overrides, weak demand discipline, or frequent emergency allocation changes that are not reflected promptly in the system.

Frequently Asked Questions about Available to Promise

How is Available to Promise different from inventory available?

Inventory available usually refers to physical stock in the warehouse or stock visible in the system at a point in time. Available to Promise goes further by considering what has already been committed and what new supply is expected to arrive. ATP therefore answers the commercial question of what can still be promised, not merely the operational question of what appears to exist.

Why does supplier performance matter to Available to Promise?

Supplier performance matters because ATP often includes future receipts from purchase orders. If those receipts are late, incomplete, or unreliable, the system may promise quantity based on supply that never arrives on time. In that sense, ATP accuracy depends not only on internal planning logic, but also on procurement execution and supplier delivery reliability.

Can Available to Promise be calculated for future dates?

Yes. Many companies calculate ATP across future time buckets by combining current stock, planned production, purchase order receipts, and existing customer commitments. This forward view helps order management teams promise delivery dates and quantities beyond the current day, while also showing when additional sourcing or production action is needed to support demand.

What usually causes ATP to become unreliable?

Common causes include inaccurate inventory records, delayed updates to customer orders, late supplier deliveries, weak production schedule control, and manual overrides that are not captured in the system quickly. ATP is a cross functional result, so it breaks down when data discipline is weak in any of the connected processes.

How should procurement teams use ATP information?

Procurement teams can use ATP signals to identify categories where inbound reliability is undermining customer commitments, where supplier lead times are too long for actual demand volatility, or where additional buffering or alternative sourcing is needed. ATP should not be treated only as a sales tool. It is also a useful indicator of supply reliability and replenishment health.