Inferensys

Glossary

Available-to-Promise (ATP)

A real-time inventory and capacity check that determines the quantity and delivery date of a product that can be committed to a customer order without creating a stockout.
Wide-angle shot of a modern WeWork open floor plan with creative walls covered in AI system architecture diagrams, product team collaborating in standing desk area with industrial lighting.
ORDER PROMISING LOGIC

What is Available-to-Promise (ATP)?

A real-time inventory and capacity check that determines the quantity and delivery date of a product that can be committed to a customer order without creating a stockout.

Available-to-Promise (ATP) is a real-time order promising function that calculates the uncommitted portion of a company's inventory and planned production, providing a precise quantity and delivery date that can be reliably quoted to a customer. It performs a netting calculation, subtracting existing demand allocations and reservations from the total supply picture—including on-hand stock, scheduled receipts, and planned production orders—to generate a positive available balance for a specific date.

The ATP check is the foundational logic within an Order Promising Engine, executing against a defined ATP Horizon to prevent overselling. Unlike a simple stock status lookup, ATP dynamically evaluates the timing of supply and demand, often using Sourcing Rules to search across multiple distribution centers. This ensures that every commitment is backed by a physical or projected inventory reality, directly protecting the On-Time In-Full (OTIF) performance metric.

ORDER PROMISING LOGIC

Core Characteristics of an ATP System

An Available-to-Promise (ATP) system is a real-time decision engine that determines whether on-hand inventory and scheduled supply can fulfill a customer order by a specific date. The following characteristics define a robust, enterprise-grade ATP implementation.

01

Real-Time Inventory Netting

The foundational calculation that subtracts gross demand (sales orders, reservations) from scheduled receipts (purchase orders, production runs) and on-hand inventory to compute a projected available balance. This netting logic runs synchronously during order entry to provide an immediate, date-specific promise without creating a stockout. The calculation respects the Demand Time Fence (DTF), where actual orders fully consume the forecast.

02

Multi-Level Supply Search

A Global ATP capability that searches for availability across a network of plants, distribution centers, and in-transit inventory. The search follows configurable sourcing rules that dictate the sequence of supply locations to evaluate. Multi-sourcing optimization evaluates all possible combinations to minimize total landed cost. The system can also traverse the supersession chain to automatically substitute discontinued items with their defined replacements.

03

Constraint-Based Evaluation

Advanced ATP systems extend beyond material availability to evaluate capacity and transportation constraints simultaneously. Constraint-Based ATP uses a constraint solver to generate a feasible delivery date that respects finite capacity scheduling limits on work centers, labor, and tooling. This prevents over-promising against a bottleneck resource and ensures the committed date is executable on the factory floor.

04

Allocation and Reservation Logic

The system enforces allocation management policies that reserve inventory for specific customers, channels, or product segments before the ATP check runs. During order entry, order reservation creates a hard or soft link between a specific quantity of supply and the customer demand, guaranteeing availability. Rule-Based ATP applies configurable business rules—such as customer hierarchies or sourcing priorities—to determine how constrained supply is allocated.

05

Backorder and Splitting Automation

When an order cannot be fully promised from a single location by the requested date, the system triggers backorder processing workflows. This includes order splitting, which divides a single order line into multiple shipments from different locations or at different times to optimize fulfillment speed. The system automatically re-promises backordered quantities as new supply becomes available, maintaining a prioritized queue of unfulfilled demand.

06

What-If Simulation Capability

An ATP Simulation environment allows planners to test hypothetical supply or demand changes without affecting live commitments. Planners can model scenarios such as a delayed purchase order, a surge in demand, or a plant shutdown to assess the impact on order promising outcomes. This capability supports proactive risk management and enables data-driven decisions before changes are committed to the operational system.

ATP EXPLAINED

Frequently Asked Questions

Clear, technical answers to the most common questions about Available-to-Promise logic, its mechanisms, and its role in modern order fulfillment.

Available-to-Promise (ATP) is a real-time inventory and capacity check that determines the exact quantity and delivery date of a product that can be committed to a customer order without creating a stockout. The ATP calculation performs a netting logic by subtracting confirmed demand (sales orders) and forecasted demand from the total supply, which includes on-hand inventory, scheduled receipts (purchase orders and production runs), and sometimes in-transit inventory. The system projects the projected available balance forward in time across the ATP horizon, identifying the first period where sufficient unallocated supply exists. When a new order inquiry arrives, the order promising engine executes this check instantly, reserving the quantity and returning a reliable delivery date. This prevents overselling and ensures that every commitment is backed by a physically or logically available asset.

ORDER PROMISING LOGIC COMPARISON

ATP vs. CTP vs. PTP: Key Differences

A technical comparison of the three primary order promising methodologies, detailing their scope, constraints, and business objectives.

FeatureAvailable-to-Promise (ATP)Capable-to-Promise (CTP)Profitable-to-Promise (PTP)

Primary Objective

Commit delivery dates without causing stockouts

Commit delivery dates considering production capacity

Commit delivery dates that maximize margin and customer value

Core Constraint Evaluated

On-hand and scheduled inventory

Inventory plus production capacity and material availability

Inventory, capacity, and total fulfillment cost vs. margin

Evaluates Production Capacity

Evaluates Financial Profitability

Typical Calculation Speed

< 1 sec

1-30 sec

1-60 sec

Primary User

Order Management Clerk

Production Planner

Customer Experience Director

Integration Requirement

Inventory Management System

Inventory + MES/Production Scheduler

Inventory + MES + Cost-to-Serve Model

Key Output

Available quantity and earliest ship date

Feasible quantity and achievable delivery date

Optimal fulfillment location and profit-optimized date

Prasad Kumkar

About the author

Prasad Kumkar

CEO & MD, Inference Systems

Prasad Kumkar is the CEO & MD of Inference Systems and writes about AI systems architecture, LLM infrastructure, model serving, evaluation, and production deployment. Over 5+ years, he has worked across computer vision models, L5 autonomous vehicle systems, and LLM research, with a focus on taking complex AI ideas into real-world engineering systems.

His work and writing cover AI systems, large language models, AI agents, multimodal systems, autonomous systems, inference optimization, RAG, evaluation, and production AI engineering.