IBNR means “Incurred But Nor Reported” and refers to claims that have occurred but where the paperwork has not been yet performed and the insurer is still unaware of them. As these claims still have to be paid out to victims or beneficiaries, insurers need to set aside money (“reserves”) to cover their soon-to-be-discovered costs, hence IBNR Reserves or simply IBNRs. Since the insurer knows neither how many of