The fiscal deficit - or the shortfall in the government's income compared with its spending - is already under strain after the government last month cut corporate tax rates. While announcing the reduction in corporate tax rates, Finance Minister Nirmala Sitharaman said the Centre was "conscious of the impact all this will have on our fiscal deficit".

"The total gross GST revenue collected in the month of September, 2019 is Rs. 91,916 crore of which CGST is Rs. 16,630 crore, SGST is Rs. 22,598 crore, IGST is Rs. 45,069 crore (including Rs. 22,097 crore collected on imports) and cess is Rs. 7,620 crore (including Rs. 728 crore collected on imports)," the Finance Ministry said in a release.

The total number of GST returns filed for the month of August (up to September 30) stood at Rs 75.94 lakh.

The government has transferred Rs. 21,131 crore to Central-GST (CGST) and Rs 15,121 crore to State-GST (SGST) from Integrated-GST (IGST) as regular settlement.

The gross GST collections comprised of Rs 16,630 crore collection through CGST, Rs 22,598 crore in State-GST and Rs 45,069 crore through IGST.

The total revenue earned by the central government and the state governments after regular settlement in September was Rs. 37,761 crore for CGST and Rs. 37,719 crore for the SGST, it said.

During April-September, the domestic component has grown by 7.82 per cent, while the GST on imports has shown negative growth and the total collection has grown by 4.90 per cent, it added.

With government already committed to scaling up public spending to boost the sagging economy, lower GST collection could change its fiscal math.

The government needs an average monthly collection of more than Rs 1 lakh crore every month to meet its budget target.