Restriction on furnishing outward supplies: GSTR-1/IFF blocked if requisite GSTR-3B filing not completed for prior period. The amendment bars registered persons from furnishing outward-supply details in FORM GSTR-1 or through the Invoice Furnishing Facility if they have not furnished FORM GSTR-3B for required preceding periods. It applies generally to those lacking GSTR-3B for the two preceding months, to quarterly filers lacking the preceding tax-period return, and to persons already restricted in using the electronic credit ledger who have not furnished the preceding tax-period GSTR-3B.