Basically the buyer asking for Compliance Plate
A Compliance Plate carries details like Date of Inspection or Installation, Vehicle Number, Chassis Number, CNG CTL No, Type, Installation Center and Unique Compliance Certificate Number and is fitted in the engine bay of the car closer to the chassis.
You can contact any Government authorized Fitment center for issuance by submitting
> RC Copy with CNG been endorsed in it
> Insurance with Endorsed CNG in Fuel type
> copy of Original Invoice of Car referring CNG as Fuel Type
CNG Fitment Center will do testing and inspection as per prescribed guidelines. If vehicle found fit for same without any leakage or issue - CNG Compliance plate been issued.
They charge in around Rs 500 to Rs 700 per inspection as baseline figure