Sir,
At the very outset, I wish to comment that in GST "marketability" is not the measure for payment of GST. However, when manufacturing process is undertaken, waste may be generated, which is disposed of falls within the definition of "outward supply" given at Section 2(83) of CGST Act, 2017 and disposal of is also included in "Supply" under Section 7(1) of CGST Act, 2017. The disposal of goods (waste) is also covered under Section 17 (5) (h) of CGST Act, 2017.
In view of above, the said waste when disposed of without payment of GST, ITC proportionate to waste disposed of is required to be reversed.
Our experts may like to offer their comments in the matter.
Thanks,
With Regards