The Fire Brigades Union (FBU) estimates that over 10,000 former retained firefighters in the UK may be owed significant pension payments. The FBU alleges that these firefighters, who were not full-time employees but were on-call, were not properly enrolled in pension schemes, resulting in potentially substantial financial losses for them in retirement. The union is urging affected individuals to come forward and is advocating for a review of pension policies to ensure all retained firefighters receive their due entitlements. The scale of the potential underpayment could amount to thousands of pounds per firefighter.