Amanda-Jane/Interested Readers:

Starting Point - National Insurance Numbers are generally issued on request, meaning you have to visit the relevant office in person to apply for one and provide proof of identity. The exceptions to this involve persons with Refugee Status/Asylums Seekers granted leave to remain in the UK and Foreign Nationals/Students with long-term Resident visas that include the right to work in the UK - those persons are sometimes issued with NI Numbers by relevant Authorities satisfied their identity has been sufficiently established.

Answers -

(i) Subject to the above only UK Citizens or persons with valid UK Work Permits/Permissions can obtain an NI Number. Persons under current UK School Leaving Age cannot apply for an NI Number. Given this, no, not everyone in the UK has one. illegal Immigrants/Migrants and in some cases members of the Irish Traveler Community..

(ii) NI Numbers cannot be shared and each is unique to a particular person. Fakes/Forgeries do exist however, so it is possible a genuine NI Number could appear on a faked NI Card, or be used by someone who knew it on an fraudulently completed application or official form. Commonly known as Identity Theft.

(iii) See above. Each genuine number is unique to a particular person and therefore can be traced back to that person. This is in fact the whole purpose of the number, to prove that person is entitled to National Insurance and associated State Benefits/Services.

(iv) See above. Apart from fakes/forgeries no NI Numbers are duplicated, each one is different.

Hope this helps while your waiting for the Authority to respond.

Becky