If the GST refunds are not presented within the established period, it will be responsible for the payment of interest and a surcharge for the delay.

The interest is 18% per year. The taxpayer must calculate it on the amount of the tax pending payment. The period of time will be from the next day of presentation until the date of payment.

Charges for late payments is Rs. 100 per day by law. So it's 100 under CGST and 100 under SGST. The total will be Rs. 200 / day. The maximum is Rs. 5,000 There is no late payment in IGST.

Latest Update as on 31st Dec 2018

Charges for the delay in the GSTR-1, GSTR-4, GSTR-3B presented for the period between July 2017 and September 2018 between December 22, 2018, and March 31, 2019.

Late fees of Rs 50 per day of delay (Rs 20 for the return of NIL) apply for those who submitted the GSTR-3B after the expiration date stipulated for the months of July 2017 to September 2018 before 22 December 2018

Update as on 7th March 2018!

CBEC withdraws the reduction in late charges only for the GSTR-5A charged for the delay in filing returns as of March 7, 2018.

This means that the late fees that taxpayers must pay for the late submission of GSTR-5A now amount to a total of Rs. 200 per day of delay (Rs 100 per day of delay for the return of NIL) subject to the maximum limit in the delay charges in Rs. 5,000

As of March 7, 2018, reduced late fees for other returns such as GSTR-1, GSTR-3B (October 2017 onwards), GSTR-4, GSTR-5, and GSTR-6 remain valid.

There are prescribed formats for each of the above returns. The forms may seem complex and difficult to understand.