GST late fee extension permits waiver or reduction for Form GSTR-4 filings submitted within the extended concession period. Amendment substitutes the earlier notified deadline with a later date to extend the concession allowing waiver or reduction of late fee for non-filing of Form GSTR-4 for 2017-18 and 2018-19, on condition that returns are filed within the extended period; the amendment is deemed effective from the original deadline so the extended concession applies retrospectively.