Material movement from one unit to another unit for further processing under gst

Chandra Shekar Yeldhandi (21 Points)

24 July 2017  
A Mfg company having 2 separate units involved in same business with same GST number. Now they need to send some materials from one unit to another unit for further processing purposes and the same will be bring back after the process.

In this case what type of documents to be maintained for sending material to another unit and bringing back under gst.