Presumptive taxation under section 44AE: calculation based on gross vehicle weight for goods carriages, unladen weight for tractors and road-rollers. Computation under section 44AE must follow Motor Vehicles Act definitions: a heavy goods vehicle is a goods carriage whose gross vehicle weight exceeds 12,000 kilograms; tractors or road-rollers are assessed by unladen weight. Presumptive income is Rs. 1000 per ton of gross vehicle weight per month for heavy goods vehicles, and Rs. 1000 per ton of unladen weight per month for tractors and road-rollers where gross vehicle weight does not apply.