units which are not availing any exempition, means they are availing input credit on raw materials,
inputs on which credit has been availed are to be sent to job worker under Rule 4(5)a of CCR 2004.
as the scraps so generated are product/bye product / part of inputs on which input credit has been availed, so the principal manufacturer ( who is sending goods for job work) has to clear the scrap so generated on "payment of duty", and to reconcile the quantity send and quantity received by the sender, the scrap portion would generate difference in stocks.
say A sent 1000 kgs of inputs to B for job worker
B produced 20 nos of finiish/ semi finish goods consuming 930 kgs of such inputs, scrap generated 70 kgs
now at the time of return of such materials B has to give statement that 20 nos goods are made on job work basis from 1000 kgs inputs, 930 kgs remains in goods, while 70 kgs is scrapped.
these 70 kgs has to be cleared by principal on payment of duty at invoice value, otherwise he would face trouble at audit stage, and such shortage would result reversal of input credit in proportionate ratio, where the value would be input value itself.