The most usual BMS divides drivers by classes, where each class has its own discount or surcharge that is applied to the basic premium. A claim-free year implies in a decline of one or more degrees on the Bonus/Malus class table on the anniversary of the contract. A claim entails an increase of a given number of degrees on the Bonus/Malus scale on the anniversary of the contract. Generally, one degree corresponds to a 5% discount or surcharge. The starting class may depend on the driver's age, sex, place of residence, the car's horsepower. Each country has a different legislation, which rules how many degrees an insurer may increase or decrease, the maximum bonus or malus allowed and which statistics insurers can use to evaluate the starting class of a driver.
