Insurers will apply a clause in your policy called average. Essentially this means that if you insured your contents for £20,000 and they were actually worth £30,000, you are underinsured by 1/3. As a result if you put in a claim for £10,000 the insurers would only have to pay you 2/3 of the claim (assuming it was valid etc), therefore you would receive a claims settlement of £6,666, not the £10,000. As a result it is important that you insure for the correct amount. Underinsuring will result in any claims being restricted on their payout. This clause is very common in domestic policies, but not many people actually know about it... until they have to claim and have got their sums wrong...don't say you've not been warned!