An endorsement can be applied to a policy to either extend or reduce the cover provided by the policy.
For example, if building work is being carried out on your home, the building under construction warranty will apply which will restrict the cover provided during this time.
An endorsement may also apply to make sure a certain action has been taken by the insured.
For example, if a driver on the policy has a medical condition that may affect their driving, the medical condition declaration will apply which states that the driver requires a medical cert confirming that they are fit to drive and they have notified the licencing authority.
They can be added at the start of the policy or mid-year if new information is given.