SD Availability Check Part 1: What ATP Does and Why It Matters

📌 KEY POINTS
✅ ATP = available-to-promise: what can still be promised to a new requirement after considering stock, planned receipts and existing issues.
✅ The check runs per schedule line: it confirms the requested quantity on the requested date, a later date, partially, or not at all.
✅ Delivery and transportation scheduling work backwards from the requested delivery date to the material availability date the ATP check needs.
✅ ATP runs in the sales order (checking rule A) and again at delivery creation (checking rule B).
⚠️ Physical stock ≠ available quantity: stock already promised to earlier orders or deliveries is not available.

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▶ WHAT THIS SERIES COVERS
Part 1: What ATP does and why it matters
Part 2: Configuring the classic availability check
Part 3: Scope of check and replenishment lead time
Part 4: Classic backorder processing and rescheduling
Part 5: aATP product availability check in S/4HANA
Part 6: Product allocation
Part 7: Alternative-based confirmation
Part 8: aATP backorder processing
Part 9: Troubleshooting ATP and aATP
Part 10: Architecting availability check at scale

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▶ 1. THE ATP IDEA

• Available = stock + planned receipts − planned issues (orders, deliveries, reservations), per date.
• Cumulative ATP over time decides what a new requirement can get.

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▶ 2. WHAT THE USER SEES

• Requested schedule line (customer wish).
• Confirmed line(s): full, partial, later date, or zero.
• Availability screen with delivery proposal (one-time delivery, complete delivery, delivery proposal).

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▶ 3. SCHEDULING

• Backward: requested delivery date − transit time − loading − pick/pack → material availability date.
• If not available then: forward scheduling from the date material is available.

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▶ 4. WHERE ATP RUNS

• Sales order creation/change (checking rule A).
• Delivery creation (checking rule B).
• Rescheduling / backorder processing (redistribution).

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▶ 5. WHAT CONTROLS IT

• Schedule line category and requirements class switch ATP on.
• Checking group (material) + checking rule (transaction) define scope (Parts 2–3).
• S/4HANA: advanced ATP adds allocation, alternatives and BOP (Parts 5–8).

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▶ STEP BY STEP

1. Check stock in MMBE and ATP in CO09.
2. Create an order for more than available.
3. Read the availability screen and confirmed lines.
4. Create a second order and see how the first one reduces ATP.

✅ CHECKPOINT: you can explain why the second order confirms later although stock seems sufficient in MMBE.

A distributor promised dates from MMBE stock in phone calls, then entered orders later. Customers were told "in stock" while the system confirmed next month, because earlier orders had already consumed the stock. Sales was trained to promise only from the order's confirmation (or CO09), and a Fiori order entry app with immediate ATP result replaced the phone-and-enter-later practice.

• Promising from physical stock instead of ATP.
• Ignoring the difference between requested and confirmed schedule lines.
• Forgetting that deliveries check again (rule B).
• Assuming ATP creates procurement — it only checks; MRP plans.
• Ignoring scheduling times when judging dates.

• Promise dates only from ATP results.
• Monitor unconfirmed quantities.
• Keep scheduling master data (routes, times) accurate.
• Explain ATP basics to sales users.
• Use CO09 for availability questions.

Questions: "What is ATP?", "What happens if stock is insufficient?", "Where does the availability check run?"
Strong answer: ATP = stock + receipts − issues per date; confirmation per schedule line, partial/later/none; backward/forward scheduling; runs in order (rule A), delivery (rule B), rescheduling; controlled by schedule line category, requirements class, checking group and rule; aATP in S/4HANA.