Chassis number is the end part of your Vehicle Identification Number (VIN). The chassis number is actually your vehicle's serial number. You have to find this number out if you plan to sell the car or buy its spare parts. The chassis number can be found in different places, depending on your car model.
Look for a rectangular plate containing the chassis number under the bonnet, beside the ABS unit.
Open your car's bonnet and find a metal plate on top of the radiator in front of the engine compartment. Open the bonnet by pulling on the lever that is usually found by the driver's door.
Take a look at the original books that came with your car. You will most likely find the chassis number there.