What is Available-to-Promise (ATP)?

Available-to-Promise, or ATP, is the number an OMS exposes to a channel to indicate how many units of a SKU can actually be delivered against a new order, given current stock, allocations, open orders, and inbound supply. It is the difference between raw on-hand and a credible promise to the customer.

Definition

ATP is calculated continuously from physical inventory across all nodes minus reservations for open orders, BOPIS pickups, pre-orders, and channel allocations, plus planned inbound where policy allows. The OMS may compute ATP per channel, per region, or per fulfillment node, and it surfaces the result through APIs that the storefront API and marketplace connectors consume. Calculations often run as event-driven jobs: every order, return, stock receipt, or allocation change emits an event that updates the relevant ATP figures, with webhooks pushing fresh values to downstream systems.

Why it matters

ATP is the contract between operations and the customer-facing front. Set it too high and the brand oversells, leading to cancellations, refund cost, and reputational damage. Set it too low and conversion drops, because shoppers see out-of-stock messages for units that physically exist. A composable OMS lets teams tune ATP rules per channel — for example, more aggressive on the owned storefront than on third-party marketplaces — and align them with strategic goals like loyalty programs, B2B service levels, or D2C launches.

Use cases

A multi-channel apparel brand exposes a single network-wide ATP figure on its storefront, drawing on DC, store, and drop-ship stock through DOM. A consumer electronics player uses different ATP horizons per region, reflecting customs and transport times for cross-border lanes. A marketplace seller publishes lower ATP values on third-party platforms to protect its own storefront during peak periods such as Cyber Week. In each case, ATP is the metric that ties inventory allocation, sourcing, and fulfillment to the promise rendered on the product detail page and the conversion funnel that follows.

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