Credit of duties in transit allowed where invoice recorded within prescribed period; extension available and statement required. A registered taxable person may take credit in the electronic credit ledger for duties or taxes on inputs or input services received on or after the appointed day though the tax was paid before that day, if the invoice or tax document was received or recorded in the books within thirty days of the appointed day, with the thirty day period extendable once by the competent authority for sufficient cause; the person must furnish a prescribed statement for such credit.