National Insurance number
The National Insurance number is used as a reference number in the Pay As You Earn system, and also by the self-employed. It is also used in applications for Individual Savings Accounts (ISAs), to check that an individual has opened only one ISA in a tax year.
British National (Overseas)
British Nationals (Overseas) are subject to immigration controls and have neither the right of abode or the right to work in the United Kingdom. BN(O)s are required to pay a "health surcharge" to access National Health Service benefits when residing in the UK for longer than six months. They are also ineligible for the Registered Traveller service, which enables expedited clearance through British immigration, despite HKSAR passport holders being eligible.