US: Deliberate failure of an applicant for insurance to reveal a material fact to the insurer.
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Failure by the insured to reveal certain facts he knows that are not such common information that the Insurer should also know them. Except in ocean marine Insurance an Insurer must prove intent and materiality to deny a claim based on concealment. Concealment is material if the facts concealed would have caused the Insurer either not to write the Insurance or to write it under substantially different terms.
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UK: The wilful failure to disclose a material fact before the insurance contract is concluded. It is a breach of utmost good faith rendering the contract void ab initio and entitling the insurer to sue for damages for deceit. If fraud is proved the insured is not entitled to a return of premium.