SAP Note 27169 - Subcontract order: Rounding error in component qty

Symptom:

A bill of material contains a component with a non-integral number of pieces for each unit of measure. (example: 1 pc of material B is needed for 10 KG of material A). When you create a subcontract order, the required component quantity is rounded correctly. However, if you change the quantity ordered, the component quantity is adjusted on the basis of this rounded quantity. As a result, the rounding becomes more and more inaccurate, that is, if you repeatedly change the quantity it significantly differs from the quantity defined in the bill of material.

Cause and prerequisites

The effect cannot be avoided in the current implementation. The conversion routine cannot always access the initial BOM because the component quantities can be changed manually in the purchase order. Since the unrounded quantity is not stored internally (it would also have to be written to the database), rounding errors cannot be avoided. For reasons of performance, you also cannot always execute a new BOM explosion in the purchase order. A satisfactory solution would be extremely complicated.

Solution
However, the user can start the BOM explosion manually and correct the resulting rounding errors when changing the purchase order quantity. For this, the function Item -> Components -> New BOM explosion is available (please also see note 16029).

Additional key words

Subcontracting component
Subcontract requisition, subcontractor scheduling agreement
ME21, ME22, ME51, ME52, ME38