Interest relief for late GST returns: temporary nil-interest windows for specified taxpayers, followed by standard interest thereafter. Amends the Union Territory GST proviso to prescribe nil interest for limited windows and a subsequent fixed interest rate for registered persons who fail to furnish FORM GSTR-3B and pay tax by the due date for tax periods February 2020 to July 2020. Relief is allocated by classifying taxpayers by aggregate turnover and by groups of states and union territories, with specific nil-interest cutoff dates per month and group, after which the stated interest rate applies for the remainder of the transitional period.