N.Y. Veh. & Traf. Law § 416
Upon the sale or lease of a motor vehicle or motorcycle the vendee or lessee shall be allowed to operate the same upon the public highways for the period of five days after taking possession thereof, without carrying number plates issued upon a registration under section four hundred one, if a motor vehicle, or under section four hundred ten, if a motorcycle, provided the motor vehicle or motorcycle shall have attached thereto and displayed thereon, in the manner therein provided, a set of dealer's, manufacturer's, or transporter's number plates issued to the vendor or lessor under section four hundred fifteen, and if a proper application for registration and number plates for such vehicle, under the provisions of section four hundred one or four hundred ten of this title, as the case may be, shall have been mailed or presented to the commissioner, or agent, accompanied with the payment of the required fee within twenty-four hours after he or she has taken possession thereof. If the motor vehicle or motorcycle is to be registered in a jurisdiction other than the state of New York, the requirement for filing or presenting such application shall not apply.
No person shall operate or drive upon the public highways any motor vehicle or motorcycle on which is fastened or displayed any such dealer's, manufacturer's, or transporter's number plates after a sale or lease of such vehicle by the dealer or lessor, except in compliance with the foregoing provisions.
A vendee or lessee to whom number plates are delivered or by whom they are held under the provisions of this section shall return the same, and the accompanying registration certificate, to the dealer or lessor before the expiration of six days after he or she took possession of the motor vehicle or motorcycle purchased or leased. If number plates so delivered or held, or such certificate, are not returned within the time above limited, the dealer or lessor shall immediately notify the commissioner of that fact by mail, describing the plates according to the general and distinctive numbers and characters thereon.
The provisions of this section shall apply also to the sale or lease of a trailer and to the use by the vendee or lessee of dealer's, manufacturer's, or transporter's number plates on the trailer sold or leased, and for the purpose of applying such provisions a trailer shall be deemed to be a motor vehicle.
N.Y. Veh. and Traf. Law § 416