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.
Glossary
Available-to-Promise (ATP)

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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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ATP vs. CTP vs. PTP: Key Differences
A technical comparison of the three primary order promising methodologies, detailing their scope, constraints, and business objectives.
| Feature | Available-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 |
Related Terms
Master the core concepts that extend and operationalize Available-to-Promise (ATP) logic to build a resilient, profitable order fulfillment strategy.
Capable-to-Promise (CTP)
Extends ATP beyond on-hand inventory to evaluate production capacity and material availability. CTP determines if a product can be manufactured and delivered by a requested date, creating a feasible production schedule in real-time. - Key Check: Bill of materials explosion and routing analysis - Use Case: Make-to-order environments where finished goods are not stocked - Benefit: Prevents overpromising when inventory is zero but production is possible
Profitable-to-Promise (PTP)
Evaluates the financial viability of an order before committing inventory. PTP balances fulfillment costs, margin, and customer lifetime value to accept or reject orders dynamically. - Key Inputs: Cost-to-serve model, freight rates, payment terms - Decision Logic: Accept, re-price, or propose alternative fulfillment - Outcome: Protects margin in low-inventory, high-demand scenarios
Demand Pegging
The process of linking a specific supply receipt (purchase order, production run) to a specific customer order. This creates end-to-end traceability for impact analysis. - Forward Pegging: Tracks where supply is allocated - Backward Pegging: Identifies which supply fulfills a demand - Critical For: Assessing the blast radius of a supply disruption
Global ATP
Searches for availability across a network of multiple plants and distribution centers to find the optimal fulfillment location. Global ATP evaluates sourcing rules, transportation costs, and lead times simultaneously. - Capability: Multi-site inventory visibility in a single check - Optimization: Minimizes total landed cost or delivery time - Enables: Omnichannel scenarios like ship-from-store
Constraint-Based ATP
An advanced promising method using a constraint solver to simultaneously evaluate material, capacity, and transportation limitations. Unlike rule-based approaches, it finds a globally feasible solution. - Variables: Machine throughput, labor shifts, carrier capacity - Output: A realistic, executable delivery date - Differentiator: Avoids sequential bottleneck failures
ATP Netting Logic
The core calculation that subtracts gross demand requirements from scheduled receipts and on-hand inventory to compute the projected available balance. - Formula: Projected Available = Prior Period Available + Scheduled Receipts - Gross Requirements - Time Buckets: Calculated daily or weekly over the ATP horizon - Variants: Discrete ATP vs. Cumulative ATP for large order evaluation

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.
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