Interest rate concession for delayed GST returns waives interest for specified taxpayers initially, then applies standard interest thereafter. Amendment prescribes the rate of interest for registered persons required to furnish FORM GSTR-3B who fail to file returns and pay tax for specified months, by classifying taxpayers by aggregate turnover and principal place of business, providing initial nil-interest periods varying by class and tax period and a uniform interest rate thereafter; the notification is deemed effective from the stated effective date and amends the principal State Tax notification of 2017.