View source for Definition:Incurred but not reported (IBNR)

📊 '''Incurred but not reported (IBNR)''' is an actuarial estimate representing [[Definition:Claims | claims]] that have already occurred but have not yet been filed with the [[Definition:Insurance carrier | insurer]]. In insurance accounting, IBNR is one of the most critical components of a company's [[Definition:Loss reserves | loss reserves]], because it captures the financial obligation for events — injuries, property damage, liability incidents — that policyholders either do not yet know about or have not yet had the opportunity to report. Long-tail lines such as [[Definition:Workers' compensation insurance | workers' compensation]], [[Definition:Professional liability insurance | professional liability]], and [[Definition:General liability insurance | general liability]] tend to carry especially large IBNR balances because months or even years can elapse between an occurrence and a formal claim notification.

⚙️ [[Definition:Actuary | Actuaries]] estimate IBNR using a combination of statistical methods — most commonly [[Definition:Loss development factor | loss development factors]], the chain-ladder technique, and the Bornhuetter-Ferguson method. These approaches analyze historical patterns of how claims emerge over time after a policy period closes, then project the remaining volume and cost of unreported events. The resulting IBNR figure is booked as a [[Definition:Liability | liability]] on the insurer's balance sheet and is subject to ongoing review as new data becomes available. Regulatory bodies such as the [[Definition:National Association of Insurance Commissioners (NAIC) | NAIC]] require carriers to demonstrate that their IBNR reserves are adequate, and independent [[Definition:Actuarial opinion | actuarial opinions]] are typically mandated as part of the annual [[Definition:Statutory reporting | statutory reporting]] process.

💡 Getting IBNR wrong can destabilize an entire insurance operation. Underestimating the reserve leaves a carrier financially exposed when late-reported claims finally surface, potentially triggering [[Definition:Solvency | solvency]] concerns or prompting intervention by state [[Definition:Insurance regulator | regulators]]. Overestimating it, on the other hand, locks up capital unnecessarily and depresses reported [[Definition:Underwriting profit | underwriting profit]], which can erode investor confidence and distort [[Definition:Rate filing | pricing decisions]]. For [[Definition:Reinsurance | reinsurers]] and [[Definition:Insurance-linked securities (ILS) | ILS]] investors, the accuracy of a cedent's IBNR assumptions directly affects the valuation of portfolios they assume. In an era of growing data sophistication, many [[Definition:Insurtech | insurtech]] firms are developing predictive analytics platforms designed to refine IBNR estimation, aiming to reduce the uncertainty that has long surrounded this essential but inherently imprecise reserve.

'''Related concepts'''
{{Div col|colwidth=20em}}
* [[Definition:Loss reserves]]
* [[Definition:Case reserve]]
* [[Definition:Loss development factor]]
* [[Definition:Actuarial opinion]]
* [[Definition:Claims management]]
* [[Definition:Reserving risk]]
{{Div col end}}