NCD is a no-claim discount, and you are entitled to it if there has been no claim on your policy for a year or more. An NCD reduces your premium for the following year and is a reward for staying accident-free.
Making a claim does not automatically disqualify you from no-claim discounts. You may still be entitled to it if your liability in an accident with an unidentified vehicle is at 20% or below. In cases where your liability is higher than 20%, your NCD might be reduced, unless you have a NCD protector cover.
NCD is why drivers often prefer to settle smaller accidents privately.