## 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**

10. Click **New → New UOM Conversion**.
11. Add the **new Inventory UOM** you want to assign to the part and save.
12. 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.

13. Save and minimize the screen.

**Step 3: Convert the Part to the Generic UOM Class**

14. Navigate to **System Setup → System Maintenance → Part UOM Conversion**.
15. Search for the part.
16. Select **Generic** as the UOM Class.
17. Choose the **new Inventory UOM**.
18. 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**

19. Open **Part Entry**.
20. Confirm that **Sales UOM** and **Purchase UOM** belong to the **new UOM Class**, not the old one.
21. Ensure the part setup matches the desired final configuration.

**Step 5: Clean Up the Generic UOM Class**

22. Return to the **Generic UOM Class**.
23. Go to the **UOMs** tab.
24. Delete all UOMs that belong to the **old UOM Class**.
25. Save the changes.

**Step 6: Final Conversion to the Target UOM Class**

26. Navigate again to **System Setup → System Maintenance → Part UOM Conversion**.
27. Search for the part.
28. Select the **final UOM Class** you want to assign.
29. Choose the final Inventory UOM (now with the correct conversion factor).
30. 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.