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Mastering UOM Changes in Epicor: A Step-by-Step Workaround Guide

A Practical Workaround for Parts with Existing Transactions


Changing the Unit of Measure (UOM) Class or Inventory UOM for a part in Epicor is not straightforward once transactions already exist. In standard scenarios, Epicor restricts these changes to protect data integrity, which can become a challenge when business requirements evolve.


Epicor provides a lesser-known workaround using the Part UOM Conversion program. While effective, this process requires careful planning, strict prerequisites, and, when changing UOM classes, the creation of a temporary (dummy) UOM class to bridge the conversion.


This guide is written for Epicor administrators and power users and outlines:


  • Mandatory prerequisites before starting

  • How to change only the Inventory UOM

  • How to change both the UOM Class and Inventory UOM using a Generic UOM Class


Following these steps carefully will help ensure a successful conversion while maintaining system integrity.


Mandatory Prerequisites

Before making any changes, both of the following conditions must be met:


  1. No on-hand quantity exists for the part.


  2. No open demand exists for the part, including:

    • Sales Orders

    • Jobs

    • Packing Slips

    • Allocations

    • Requirements

If any of the above exist for the current UOM, Epicor will prevent the change.


Option 1: Changing Only the Inventory UOM (Same UOM Class)

Use this option if the UOM Class will remain the same and only the Inventory UOM needs to change.


Steps

  1. Navigate to System Setup → System Maintenance → Part UOM Conversion.

  2. Search for the part you want to update.

  3. In the Convert to UOM Class dropdown, select the same UOM Class currently assigned to the part.

  4. Choose the new Inventory UOM ID.

  5. Click Submit Conversion.


Notes

  • If there is still open demand for the current UOM, Epicor will display an error identifying where the demand exists.

  • If no demand exists, the system will apply the change and assign the new Inventory UOM.


Option 2: Changing Both the UOM Class and Inventory UOM

This option is more complex and requires creating a temporary Generic (Dummy) UOM Class to bridge the conversion.


Step 1: Create a Generic UOM Class

  1. Navigate to Material Management → Inventory Management → Setup → UOM Class.

  2. Search for the current UOM Class assigned to the part.

  3. Go to the UOMs tab and record all UOM IDs assigned to this class (mandatory).

  4. Clear the screen.

  5. Search for the new UOM Class you want to assign.

  6. Go to the UOMs tab and record all UOM IDs assigned to this class (mandatory).

  7. Clear the screen.

  8. Click New and create a new UOM Class:

    • ID/Description: Generic

    • Class Type: Other

  9. Save the new class.


Step 2: Add UOM Conversions to the Generic Class

  1. Click New → New UOM Conversion.

  2. Add the new Inventory UOM you want to assign to the part and save.

  3. Add all UOMs recorded from both the old and new UOM Classes:

    • Set the conversion factor to 1 (temporary).

Important: The Generic UOM Class must include every UOM from both classes. If one is missing, Epicor will return a UOM conversion not found error.

  1. Save and minimize the screen.


Step 3: Convert the Part to the Generic UOM Class

  1. Navigate to System Setup → System Maintenance → Part UOM Conversion.

  2. Search for the part.

  3. Select Generic as the UOM Class.

  4. Choose the new Inventory UOM.

  5. Click Submit Conversion.

If open demand still exists, Epicor will display an error. Otherwise, the part will now be assigned to the Generic UOM Class.


Step 4: Validate Part Setup

  1. Open Part Entry.

  2. Confirm that Sales UOM and Purchase UOM belong to the new UOM Class, not the old one.

  3. Ensure the part setup matches the desired final configuration.


Step 5: Clean Up the Generic UOM Class

  1. Return to the Generic UOM Class.

  2. Go to the UOMs tab.

  3. Delete all UOMs that belong to the old UOM Class.

  4. Save the changes.


Step 6: Final Conversion to the Target UOM Class

  1. Navigate again to System Setup → System Maintenance → Part UOM Conversion.

  2. Search for the part.

  3. Select the final UOM Class you want to assign.

  4. Choose the final Inventory UOM (now with the correct conversion factor).

  5. Click Submit Conversion.

 

Final Result

At this point, the part will:

  • Use the new UOM Class

  • Have the correct Inventory UOM

  • Contain valid UOM conversions

You can now resume normal processing for the part using the updated UOM structure.

 

Final Tip

This workaround is powerful but sensitive to setup errors. Always double-check:

  • No open demand exists

  • All UOMs are included in the Generic class

  • Sales and Purchase UOMs align with the final UOM Class

Following these steps carefully will ensure a smooth and successful UOM conversion in Epicor.

 
 
 
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