Interest rate relief: temporary nil-interest windows for delayed GST GSTR 3B payments, then standard interest applies. Amends the Central Tax notification to set a temporary rate of interest regime for FORM GSTR-3B filers who default on tax payment: a specified nil interest window followed by the ordinary interest rate, with nil-period end-dates varying by aggregate turnover classes and by groups of States and Union territories, and applicable to the enumerated tax months listed in the Table.