英國內政部 BNO Visa Guidance [11.4.2023]
申請人在申請BNO Visa時, 未夠18歲 (Household Child), 如果在申請 Settlement 已年滿18歲可以獨立申請 Indefinite Leave to Remain- 透過 Household Member Route 申請.  "A child who has turned 18 since they successfully applied for entry clearance or permission to stay should apply as a BN(O) Household Member at settlement. As with other adult children, they will not need to demonstrate that they continue to meet a relationship requirement." - page 53 of BNO Visa Route Guidance Source: BNO Visa Route Guidance 11 April 2023