Under-insurance means that the ‘sum insured’ is less than the cost of rebuilding, replacing or repairing the buildings or contents at the time of the loss or damage. This might meant that any claim that is settled will be reduced in proportion depending on how underinsured you are, regardless of the amount of the claim.
For example, if your amount of cover only covers a proportion of the cost of rebuilding, replacing or repairing the buildings or contents, it is likely that the insurer will only pay that proportion of the claim for repair or replacement and you will have to cover the remaining cost of the loss or damage yourself. Where there’s a severe underestimations, your insurance provider could even refuse to pay out completely.
Being under-insured is different from being uninsured. When you are uninsured you have no policy in place at all. Although this saves you money in the short term, you risk losing far more than you save if the unexpected happens.