IPTM3525 | Calculating gains: death, maturity, full surrender or assignment: related policies
From HM Revenue & Customs · Insurance Policyholder Taxation Manual
Broadly, a policy is related to another policy if under the terminology of ICTA88/SCH15/PARA17 they are ‘old’ and ‘new’ policies in relation to a termination of one policy and its substitution by another - see IPTM7515 for more details. Typically this refers to a maturity option where one policy matures and the proceeds are applied as premium for a new policy.