Tax payment at time of supply required for small taxable persons; must pay State tax on outward supplies. Registered persons below the notified small-turnover threshold, and those likely to remain below it in the registration year who have not chosen composition levy, are required to pay State tax at the time of supply on outward supplies as specified by the time-of-supply provision, including situations attracting the invoice-based rule; they must also furnish the returns and details under Chapter IX and remit tax within the payment period prescribed by the Act.