What is available to promise?

Available to promise is the quantity you can actually commit to a new order right now. It is on-hand stock minus what is already allocated to open orders and reserved for other channels, plus inbound stock arriving inside the promise window. It is nearly always a smaller number than the on-hand count.

Selling against on-hand instead of available to promise is the ordinary cause of overselling. The units are physically present; they are already owed to somebody else.

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