Understanding Epicor MRP — Why It Goes Wrong
Epicor MRP (Material Requirements Planning) runs against demand inputs (sales orders, forecasts, job demands) and generates supply suggestions (unfirm jobs, suggested POs) based on each part's planning parameters. When MRP generates garbage output, the root cause is almost always one of these three things:
- Bad part master planning parameters — wrong Order Policy, Time Phase, minimum quantity, or lead time settings
- Bad demand data — phantom sales orders, old forecasts that were never deleted, or demand outside the planning horizon
- Make/buy logic errors — a part that should be Bought is set to Make, or vice versa
Problem 1: MRP Regeneration Fails or Aborts
If MRP fails to complete, the first step is to check the MRP log:
Check the MRP Log
Navigate to Production Management > MRP > Reports > MRP Log. Review the log for the failed run — look for specific error messages, part numbers, or job numbers mentioned. Most MRP failures leave an error code that points directly to the problem.
Common MRP regeneration failure causes:
- Parts with circular BOM references — Part A requires Part B, which requires Part A. Epicor can't plan these. Find and fix the BOM.
- Orphaned job records — Jobs in a status that MRP can't process. Look for jobs in "Planned" status that are very old.
- Database integrity issues — If MRP was recently working and suddenly fails with no BOM changes, a database repair may be needed. Contact your Epicor system admin.
Problem 2: MRP Generates Hundreds of Unnecessary Unfirm Jobs
This is the most common MRP complaint. When MRP floods the suggestions queue with jobs nobody wants, the culprit is almost always part master settings.
Identify the Worst Offenders
Sort the MRP unfirm job list by part number and look for parts with an unusually high number of suggestions. These are your starting point.
Review the Part Master Planning Parameters
For each problem part, go to Part Entry > [Part] > Planning tab. Check these fields:
- Planning Type — should be MRP for parts you want MRP to plan. If it's set incorrectly, MRP may plan parts that should be manually managed.
- Order Policy — "Lot for Lot" creates one job per demand unit. "Fixed Quantity" creates jobs in batches. "Min/Max" uses quantity ranges. Pick the one that matches how you actually manufacture or buy this part.
- Minimum Order Quantity — a high minimum with a small real demand creates oversized jobs. Verify this matches supplier or production minimums.
- Lead Time — unrealistic lead times push demand signals incorrectly and cause MRP to create phantom early demand.
Changing planning parameters on a part will affect all future MRP runs. Make changes carefully and document them. A common mistake is changing parameters on a large group of parts at once — do it incrementally so you can identify the impact of each change.
Problem 3: MRP Ignores Real Demand
When sales orders or jobs exist but MRP doesn't generate supply suggestions, check these in order:
Check the Part's Planning Type
If the Planning Type on the Part master is set to anything other than MRP (e.g., Min/Max, or None), MRP will not generate suggestions for that part. This is the most common cause of "MRP ignoring demand."
Check the Time Fence and Planning Horizon
MRP respects the planning horizon set in the MRP parameters. If demand is far in the future and outside the planning horizon, MRP won't generate a suggestion yet. Also check the Time Fence — demand inside the time fence is typically excluded from auto-suggestion by MRP.
Verify the Demand Source Is Valid
Confirm the sales order or job generating the demand is in the right status. Sales orders in "Held" status or jobs that are already closed won't generate MRP demand.
Problem 4: Make/Buy Logic Errors
When MRP suggests jobs for parts that should be purchased (or POs for parts you make), the issue is on the Part master:
Go to Part Entry > [Part] > General tab. Verify the Type field — "Manufactured" parts get job suggestions, "Purchased" parts get PO suggestions. A part set to "Manufactured" that should be purchased will generate a flood of unfirm jobs instead of suggested POs.
Note that the Make/Buy setting can also be overridden at the Part Plant level. Check both the global Part record and the Part Plant record for the site running MRP.
After Fixing: Running a Clean MRP Regeneration
After correcting planning parameters or demand data, delete all existing MRP unfirm suggestions and run a full regeneration:
- Go to Production Management > MRP > General Operations > Delete Unfirm Jobs — delete all unfirm suggestions to start clean
- Run Production Management > MRP > General Operations > MRP Processing — select Full Regeneration
- Review the MRP log and the new suggestions list carefully before firming any jobs
Still Stuck? We Can Help.
If this guide didn't fully resolve your issue — or you're dealing with something more complex — our Epicor consultants are available same-day. No long-term contract required.