NCB (No Claim Bonus) is a discount offered by insurance companies on the renewal premium of a policy, as a reward for not making any claims in the previous policy period. The percentage of discount increases with every claim-free year, up to a certain limit. This means that if a policyholder does not make any claims in a year, they are entitled to a discount on their next year's premium. NCB can be transferred from one insurance company to another, in case the policyholder decides to switch insurers, provided the policy is renewed within the specified period.