GST on retro-fitment of Twin Pipe Air Brake System on Railway Wagons

In re Pew Engineering Pvt. Ltd. (GST AAR West Bengal) Whether retro-fitment of twin pipe air brake system is composite supply and what is the rate of tax thereon? The Applicant’s contract for retro-fitment of Twin Pipe Air Brake System on Railway Wagons is to be treated as Composite Supply, where the Twin Pipe Air Brake System is the Principal Supply. Twin Pipe Air Brake System is classifiable under Tariff Head 8607 21 00 and is taxable @ 5% [in terms of Serial No. 241 of Schedule I of Notification No. 01/2017 – CT (Rate) dated 28/06/2017] with no refund of the unutilized input tax credit...