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 against future tax liabilities.
Because the telco had already submitted its input tax credit details based on estimates, prior to the introduction of GSTR-2A, it sought to rectify returns in order to get a refund of the excess amount it paid. The telco had submitted its monthly Form GSTR-3B based on estimates for the period in question.