This Practice Note provides a detailed analysis of what underinsurance is, the principal causes, the remedies available to insurers where policyholders underinsure, and recent case law relevant to brokers’ duties.IntroductionUnderinsurance is one of the most persistent issues in UK property and business interruption (BI) insurance policies. The majority of policyholders insure for less than the full value of their assets and consequently expose themselves to substantial shortfalls should they need to make a claim.Despite its prevalence, there is very limited case law on underinsurance. Much of the legal framework derives from the Insurance Act 2015 (IA 2015), the Consumer Insurance (Disclosure and Representations) Act 2012 (CI(DR)A 2012), and older authorities on materiality and disclosure.For more information about IA 2015, see Practice Note: Insurance Act 2015 (IA 2015)—essentials and for more information about CI(DR)A 2012, see Practice Note: A guide to the Consumer Insurance (Disclosure and Representations) Act 2012.What is Underinsurance?DefinitionUnderinsurance occurs where the sum insured or declared value is insufficient to meet the actual loss following damage. This can occur