Aviva has urged consumers to check their policies as over the past five years it has paid out over £2.2 million in critical illness payments to customers who didn't initially realise they could claim.
The claims were identified when the customers contacted the insurer to make changes to existing policies (for example when moving house) or to apply for a new insurance plan.
Since the start of 2009, 21 claims were found on policies which were live when the customer was diagnosed with a critical illness which met the policy criteria. One case meant that the customer received £325,000 as a result of their claim.
Aviva has released the information to encourage people to check what cover they have in place, to make sure they don't miss out on valuable benefits.
Almost half of the cases identified - nine out of 21 - were for Malignant Melanoma.
Aviva said this condition has attracted attention in recent weeks, after scientists reported that they may have found a cure for more advanced cases.
Robert Morrison, chief underwriter for Aviva said: "Providers and advisers make every effort to ensure customers understand their cover, but over time people may forget exactly what they have in place. It's upsetting to think there are cases where people could benefit from their policies but don't know that they can claim.
"The good news is that in these instances we were able to see that the customers had valid claims, so we could process them retrospectively. We'd urge anyone who has a protection policy to take a few moments to check what it covers - just so they can be sure they won't miss out if the unexpected happens."
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