How to change the base unit of measure of a material when we already maintained already some stock?

Tips by: Dvj

Before changing the unit of measure is there any stock of that material avaiable? 

Base unit of can't be changed once you have created the material and there are stocks.

Any successful changes in material master only took place when there is no open document from SD, PP, MM & FI for that material.

Base unit of measurement cannot be changed.  The reason being material movement history is there in table - MSEG mainly which otherwise create inconsistency in reporting.

Instead, create new material and build stock by process in new and old materials.

1) You can only change the base units of measure under the following circumstances:
- No stocks are available for the material.
- There are no existing purchase requisitions, purchase orders, or scheduling agreements for the material.
- At present, no purchase orders or purchase order items are being created or changed.  If requests for quotations, purchasing info records, or contracts are available for a material, the system gives a warning while changing base unit of measure. Still if you want to change unit of measure specify in a dialog box the factor for converting the base unit of measure into the new base unit of measure. The purchasing info records are then, if necessary, updated.

2) If there are Open purchase requisitions, purchase orders, or scheduling agreements for the material.
--Run MM02 (Change Material Master immediately.
--Overwrite the old base unit of measure with the new one in basic data screen.
--Save the change.
--System checks

If a change criterion (MM02) is meeting all necessary prerequisites (as mentioned in point 1), system allows changing base unit of measure. Otherwise it displays warning or error. You can display the reason for this, by choosing Display Errors (ctrl+F1)

Points to note:
You can change the base unit of measure if there is no stock of the material during current and previous period. Also, there should not be any open PO's & requistions.

SAP help describes in the following manner about change of unit of measure which is self-explantory:

Diagnosis:  You wanted to change the base unit of measure. However, you can do so only under certain circumstances, including the following:

- If there are no stocks of the material in the current period and in the previous period.
- If there are stocks in the previous period, you can clear them as follows:

a) Post the stock in the previous period to the current period (for example, using movement type 561 Posting date 30.06.XX ) so that the stock for the previous period is the same as the stock for the current period.

b) Clear the stock with the posting date in the previous period (for example, using movement type 562 Posting date 30.05.XX).
- If no purchase requisitions, purchase orders, or scheduling agreements exist for the material.

Procedure :  Choose *Display errors* to see why you cannot change the base unit of measure for this material.

The pushbutton *Display errors* appears only in dialog mode, not in data transfer or in mass maintenance. If this message appears in data transfer or in mass maintenance, and you want to know why the base unit of measure cannot be changed, access the material in dialog mode using the relevant transaction below, try to change the base unit of measure as required, and then choose *Display errors*:

Lastly, you can considered an Alternate Unit of Measure to do the Conversion from KG to Liter. You then could use your Alternate Unit of Measure as your 
Purchased UoM and PLant UoM.

Given the level of activity sometimes required to change the base UOM, it often makes more sense just to add an alternative UOM on the material master. 

Maintain the relationship between the Base UOM and the new UOM on the material master and then continue to procure the material in the new UOM rather than the base UOM. If stocks exist I would think it is unlikely that their existing UOM is incorrect as they must have been receipted in that UOM at some point.

In summary:
In the Material master you can maintain the Units of measure IN Material master,
- Base unit of measure in Basic data View,
- Purchase Order Unit in view purchasing (need to activate Variable order unit)
- Sales Order Unit in view sales org 1
- Unit of Issue in view Plant/storage data1

Maintain the conversion factors for all the Unit of measures used.

SAP MM Reference Books:
SAP Material Management Interview Questions, Certification and Configuration Books

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SAP MM Purchasing

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