Yes, all claims and incidents need to be notified to future insurers. When you notify your insurer that you have had a problem at your property (for example theft, washing machine leak or DIY accident), but there is no money paid out, it is known as a reported loss. You might not have received any money because you were not covered, or because the excesses on the policy made it uneconomical for you to claim.
Insurers list these reports on industry wide exchanges to help underwriters accurately assess the risk of insuring your property. Not declaring a reported loss could lead to your policy being declared void, a claim not being paid out in full or a claim declined.