BOM Not Exploding in Purchase Order? Here's How to Fix It

If you're creating a subcontracting purchase order in SAP and notice that the BOM (Bill of Materials) isn't exploding—even though you’ve already maintained the BOM for the end product—don’t panic. You're definitely not alone. This is one of those common SAP quirks that can throw off even experienced consultants. So, what’s going wrong? Let’s walk through a practical checklist to troubleshoot and resolve the issue.

1. Double-Check Material Master Settings (MRP4 View)

Here's the thing: the system won’t explode the BOM unless specific fields are set correctly. 

Go into the MRP4 view of your Material Master and look at the “Individual/Collective Indicator” field. 

  • Set this field to “2” or leave it blank. 
  • Then go to the BOM via Tcode CS03 and in the item detail, make sure “Explosion Type” is set to “LB”. 
Both these settings work together to trigger the BOM explosion during PO creation.

2. Verify PIR (Purchasing Info Record) Has the Right Category

Now, you might be wondering—what’s PIR got to do with this? When you’re dealing with subcontracting, the PIR must have an Info Category of “3”. That’s because in a subcontracting scenario, you’re sending components to a vendor and receiving the final product. Without the correct PIR category, the system doesn’t recognize the structure properly and skips the BOM explosion.

3. Special Procurement Key Must Be Set to 30

Check the MRP2 view of your Material Master. Here’s where the Special Procurement Key comes into play. 
  • Make sure this field is set to “30”, which stands for subcontracting. 
If it’s missing or set incorrectly, the BOM won't trigger because SAP won’t interpret the order as a subcontracting type.

4. Item Category “L” Is Mandatory

Let’s not forget the basics: for BOM to explode in a PO, the Item Category in the purchase order must be “L” (which is for subcontracting). Also—this seems obvious but worth repeating—you must have a production BOM maintained for the header material. Without it, there’s simply nothing to explode.

5. Confirm the BOM Validity Period (CS03)

This one’s sneaky. Sometimes the BOM is set up correctly, but the validity period doesn’t match your PO date. 
  • Use Tcode CS03 to check the valid from/to dates for the BOM. 
  • Make sure your PO date falls within that validity range.

6. Cross-Check PO Date vs BOM Validity

Just to drive it home: if your PO creation date is outside the BOM validity window, the explosion simply won’t occur. It's an easy one to miss—especially when working across multiple materials or older master data.

Final Thought: Check Each Link in the Chain

BOM explosion issues in subcontracting POs are usually the result of one small misconfiguration. It’s rarely just one thing—it’s the cumulative effect of several settings that need to be perfectly aligned. By walking through the steps above, you’ll be able to catch what’s out of place and get your subcontracting process running smoothly again. Still stuck? Sometimes it helps to simulate the subcontracting process in a test system with a simple material to isolate the root cause.

Fast Links:
Email Purchase Order
External Send - Sending PO by email

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