What is the Bharti Airtel vs Centre GST refund case all about?

Why did Bharti Airtel demand a refund?   In October 2018, Bharti Airtel claimed that it had paid excess GST of Rs 923 crore for July-September, 2017 in the absence of a purchase-related tax return form called GSTR-2A.  GSTR-2A was not in operation during the period. It became operational in September 2018 for availing input tax credit -- the tax paid on inputs that can be adjusted agains…