Payload is specified by the vehicles manufacturer as the maximum load a vehicle can carry. It’s calculated by deducting your vehicle’s Kerb Mass from its Gross Vehicle Mass (GVM) with the difference being the maximum you can load in to your vehicle. Remember this includes all passengers and luggage, which can soon add up. So if you have an SUV with a payload of 650kg, 5 large blokes will use most of this up before any luggage has been loaded.
Ensuring you remain below a vehicles maximum payload is critical. Exceeding the payload limit will inevitably cause issues with handling, may damage the vehicle and in poor conditions the risks are multiplied. Traction will be impaired, stopping distance when breaking will increase, body roll when cornering will increase.
In the event of an accident you also are at risk of insurance companies not paying out. So please ensure you know your vehicles payload and stay within the manufacturers limits.