Use the below settings in your SAP IMG PP Setting for above issue.

Make the following settings in the order type-dependent parameters (Customizing for Shop Floor Control by choosing Master data -> Orders -> Define Order Type-Dependent Parameters) : OPL8

1. With the Cost collector indicator, you decide whether you want to collect the costs in a product cost collector. It specifies whether the costs are collected on a manufacturing order, (production order, process order), or product cost collector.

• If this indicator is turned on, the costs are collected on a product cost collector. In this case you use the functionality of Product Cost by Period. preliminary costing, simultaneous costing, and final costing are performed at the level of the product cost collector. In this case you calculate the work in process and variances by period.

 
• If this indicator is not turned on, the costs are collected directly on the manufacturing order. In this case you use the functionality of Product Cost by Order. Preliminary costing, simultaneous costing, and final costing are performed at the level of the manufacturing orders. In this case you normally calculate work in process and variances by lot.

Now, the main prerequisites for Split order are follwoing : 

An order split is allowed with the following system status:

• Header status: Partially released, released, partially confirmed 
• Operation status of the split operation and all successors: Created, released, partially confirmed

• Header status: Created, delivered, finally confirmed, locked, technically complete, closed, deletion indicator set.
• Operation status of the split operation and all successors: Finally confirmed, dispatched, partially dispatched, capacity split, capacity requirement assigned, capacity requirement partially allocated.
• Operation status of the split operation: Deleted.

To ensure that settlement is performed without any additional variances, the parent and child orders must be assigned to the same Product Cost Collector.  After an order split, the costs per piece can no longer be calculated for each order, since operations and goods movements are usually not distributed equally between parent and child. As a result, settlement by order is not supported. Settlement is performed through a product cost collector.

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