Non-disclosure means not providing important information about yourself or your property to your insurer. When you first arrange an insurance policy, and at each renewal, the law says you must tell your insurer about anything that could affect its decision to insure you; this includes whether it might impose an exclusion, or additional premium or defer cover, or change the terms on which it would offer insurance (this information is called “material information”). If you do not tell the insurer, it is called “non-disclosure”.
The remedy an insurer has when you fail to disclose material information, is to avoid or cancel the policy back to the beginning and treat it as if it never existed. One of the most serious aspects of this is that you can find yourself in a position where you have no insurance and, because of the non-disclosure, you cannot get any more insurance to replace what you had.
Where there has been non-disclosure of material information and it is found at claim time, insurers will sometimes take the action they would have taken if they had been told. This means they might reduce the cover, increase the premiums or place an exclusion on cover. However, this is a better result for you than having no cover at all.