A car insurance no claims discount (NCD) can reduce your premium when you have completed claim-free years, although the amount varies between insurers. A claim may reduce your NCD, but the effect depends on your policy and the circumstances; some policies offer protected NCD for an additional cost, subject to limits and conditions. Your insurer may ask for proof of your previous discount when you change provider, so keep renewal documents or a claims-history letter. Check the policy wording or ask an FCA-authorised insurer how its rules apply to your circumstances.