In SAP,WIP (at target cost) or Variance is posted during settlement using CO88 TCode which is last step in the cost object controlling for all the product cost collectors for a plant.
Collective Processing for Product Cost Collector
IMG MENU PATH
Accounting → Controlling → Product Cost Controlling → Cost Object Controlling → Product Cost by Period → Period-End Closing → Single Functions: Product Cost Collector → Settlement → CO88 – Collective Processing
In the following step by step guide, you will find instructions with screenshots.