Time of supply rule: small registered persons must pay central tax at supply and file prescribed returns. Notification classifies registered persons with aggregate turnover not exceeding one crore and fifty lakh rupees who did not opt for composition levy as liable to pay central tax at the time of outward supply under the time-of-supply provision, including situations covered by the supply-timing rules; such persons must furnish details and returns as required in Chapter IX and pay tax within the periods prescribed by the Act.