Tax Law, § 502
Example 1:
If a tractor, having an unloaded weight of 12,200 pounds, and a maximum gross weight of 62,000 pounds, is used either with trailer A (having an unloaded weight of 10,650 pounds and a maximum gross weight of 44,000 pounds) and trailer B (having an unloaded weight of 9,270 pounds and a maximum gross weight of 40,000 pounds), a separate permit is required for the tractor and a separate permit is also required for each trailer, since the maximum gross weight of each is in excess of 18,000 pounds.
Example 2:
If a trailer having a maximum gross weight of 16,000 pounds is used with a tractor having an unloaded weight of 3,500 pounds, separate permits are required for the tractor and trailer, since the maximum gross weight of each in combination with the other is in excess of 18,000 pounds.
Example 3:
If a trailer having a maximum gross weight of 10,000 pounds is used with a tractor having an unloaded weight of 2,500 pounds, no permit is required for either the tractor or the trailer, even if the carrier elects the unloaded weight method of computing the tax, since the unloaded weight of the tractor is not over 4,000 pounds and the maximum gross weight of each is not over 18,000 pounds.
Example 4:
If a trailer having a maximum gross weight of 10,000 pounds is used with a tractor having an unloaded weight of 5,000 pounds and if the carrier elects the unloaded weight method of computing the tax, a permit is required for the tractor but no permit is required for the trailer since its maximum gross weight is not over 18,000 pounds. If the carrier does not elect the unloaded weight method of computing the tax, no permit is required for the tractor since its maximum gross weight is not over 18,000 pounds.
N.Y. Comp. Codes R. & Regs. Tit. 20 § 470.4