Insured losses that have occurred but have not been reported to a primary insurance company. These types of claims have a tremendous effect on a reinsurance treaty, which may be showing a healthy profit when in reality it is losing money. Hence, under this false security, the re insurer will continue operating under a rating plan that is totally inadequate for the losses. This explains why a provision for incurred but not reported losses should be made in a rating plan. Also, the re insurer must establish an adequate reserve for IBNR claims to make a correct analysis of its business. If such a reserve is not established, overly optimistic evaluation of the real loss may not be revealed for several years. A method of deriving the reserve for IBNR claims is to calculate a percentage of the Claims Paid and Outstanding.