ATP and CTP in the context of APS: How GANTTPLAN APS ensures reliable delivery planning

Stronger delivery commitments – less stress in your supply chain

In today’s manufacturing landscape, the ability to make reliable delivery commitments is critical for customer satisfaction and maintaining a competitive edge. Two essential concepts that support this capability are ATP (Available-to-Promise) and CTP (Capable-to-Promise). While ATP is typically handled within the ERP system – based on stock levels and open orders – CTP takes it a step further: as a function of the APS (Advanced Planning and Scheduling) system, it also factors in production capabilities.

Both functions are vital for responding to customer inquiries with confidence, meeting delivery deadlines, and optimizing resource utilization.

This article explores how ATP and CTP work from a user perspective and how GANTTPLAN APS seamlessly integrates these capabilities into its APS system.

ATP – Availability at a glance

ATP checking is a well-established feature in ERP systems. It determines whether a product can be delivered at a specific time based on current stock levels, open orders, and planned production orders. However, it does not consider capacities such as machine availability or personnel resources. This means an order may appear available, even if actual production capabilities are lacking.

ATP (Available-to-Promise) refers to the quantity of a product that can be reliably committed to a customer, based on:

• Stock levels
• Open orders
• Planned production orders
• Reservations for other customer orders

The ATP check is performed at a specific point in time to assess whether a product is available on a given date. It does not factor in production capacity – no machine availability, no workforce consideration.

ery scheduled order is automatically ATP-validated, simplifying planning and increasing reliability.

ATP logic

The check is based on a net availability calculation:

ATP = (stock + planned receipts) − (reservations + open requirements)

Different strategies can be applied:

• First-come, first-served: Allocation follows the order of incoming requests
• Push strategy: Availability is distributed automatically
• Pull strategy: Availability is checked on demand

Limitations of ATP – A practical example

An order may be shown as “available” because the material and planned production exist—even though the production machine is down or staff are unavailable.

CTP – Can I deliver on day X?

Despite its widespread use, classic ATP checks in ERP systems have clear limitations. They focus solely on material availability and overlook critical factors like machine capacity and workforce resources. Without capacity checks, orders may appear deliverable even when production isn’t feasible.

Additionally, ATP logic is based on a static snapshot, meaning short-term changes in production or supply chains aren’t dynamically considered. In complex system landscapes, this can lead to overbooking – especially when multiple systems or manual interventions are involved.

CTP (Capable-to-Promise) enhances the ATP check by adding a crucial dimension: production capacity. While ATP verifies material availability, CTP goes further by analyzing whether – and when – a product can actually be manufactured. It considers:

• Material availability
• Machine capacity
• Workforce resources
• Existing production plans

CTP combines material and capacity checks in a single, integrated process. It simulates a company’s actual production capabilities and, if needed, can automatically suggest new production orders or reallocations to fulfill customer demand.

CTP logic

CTP operates on a dynamic planning view. It accesses production planning systems (e.g., APS – Advanced Planning and Scheduling) and takes into account:

• Available capacities (machine uptime, shifts, maintenance windows)
• Production routes and lead times
• Material flows and delivery schedules

CTP in Action – A practical example

A customer places an order for a product that’s currently out of stock. The CTP check identifies that both material and machine time will be available in three days—and returns this as a realistic delivery date.

How GANTTPLAN applies CTP

In GANTTPLAN APS, CTP checks are performed using simulation orders or additional requests. The process works as follows:

• Request from ERP: The ERP system sends a request to GANTTPLAN APS with a material number, asking: “What’s the earliest possible completion date for this order?”
• Simulated scheduling in GANTTPLAN APS: GANTTPLAN APS initiates a simulation run, including an MRP calculation. This considers replenishment times, stock levels, and other relevant factors to enable reliable planning. The order is then scheduled based on both material availability and production capacity.
• Feedback to ERP: The calculated completion date is returned to the ERP system and applied to the customer order.
• MRP Run in ERP or GANTTPLAN APS: A material requirements planning (MRP) run is executed – either in the ERP system or directly in GANTTPLAN APS for faster processing – based on the simulated completion date. The result of the run, including planned requirements and orders, is then fed back into GANTTPLAN APS.
• Final Scheduling: With updated data, GANTTPLAN APS can now schedule the order definitively, ensuring both material and capacity constraints are met.

This ensures that CTP checks are both conceptually robust and operationally reliable, thanks to tight ERP integration.

CTP instead of ATP: Real-time planning with GANTTPLAN

• Realistic delivery commitments through capacity-aware planning
• Improved delivery reliability and customer satisfaction
• Optimized use of production and logistics resources
• Reduced overbooking and fewer bottlenecks

Additional requests: Flexibility for short-term customer demands

GANTTPLAN’s additional request feature is a key enabler for CTP scenarios. It allows planners to flexibly insert extra production orders into the schedule without disrupting the main planning flow.

There are two types of additional requests:

• Without a deadline: Additional production orders are scheduled into available capacity as soon as higher-priority orders have been completed.
• With a deadline: The system attempts to meet the requested delivery date for additional production orders as closely as possible, even if they have lower priority.

Conclusion: GANTTPLAN APS combines planning with reliability

By combining automated ATP validation with simulation-based CTP functionality and integrated MRP feedback, GANTTPLAN APS provides a powerful solution for manufacturers aiming to improve delivery performance, reduce costs, and enhance planning reliability.