Available-to-Promise (ATP)
Available-to-Promise (ATP) is the availability check in the ERP that answers in real time which quantity of an item can be firmly promised for which date. ATP considers not only current stock but also planned receipts and already reserved quantities — the basis for realistic delivery dates.
What ATP actually calculates
ATP calculates the freely promisable quantity from several figures:
- Plus: physical stock on hand and planned receipts (open purchase orders, production orders)
- Minus: quantities already promised/reserved for other orders
The result is the quantity that can be promised to a new order without conflict — including the earliest possible date.
ATP vs. CTP — available vs. feasible
- ATP (Available-to-Promise): checks against existing and planned stock — "is it there or arriving as planned?"
- CTP (Capable-to-Promise): goes a step further and checks whether additional production with free capacity and material can still deliver — "can we still make it?"
CTP is more computation-intensive and usually part of APS systems (Advanced Planning and Scheduling).
ATP in ERP and sales
In the order-to-cash process, the ATP check runs right at order entry: the sales team sees immediately whether and when delivery is possible. This avoids over-promising and scheduling conflicts. Most enterprise and mid-market ERP systems offer rule-based ATP with backorder processing — for example SAP S/4HANA with advanced ATP (aATP), Microsoft Dynamics 365, Oracle, Oracle NetSuite and Infor.