Total number of national insurance numbers issued between 1997 and 2006Number19971,017,50019981,026,88519991,021,7762000995,3512001928,05920021,082,03520031,141,79520041,250,62220051,486,31220061,531,786 Note: The number of national insurance numbers (NINOs) issued includes the following: 1. Children who reach 16 years of age (the juvenile registration process); 2. UK adults who missed out on the juvenile registration process; and 3.Foreign nationals who enter the UK and require a NINO for benefit, tax credit or employment purposes (adult NINO allocation process).

The discrepancy between the number of NINOs allocated and the increase in the overall numbers of cases in issue is due to the differences in Child Reference Numbers allocated and those changing to NINOs at aged 16 years, which is closely linked to birth rates over a 16-year period.

NINOs are not normally deleted from the Departmental Central Index (DCI) or Customer Information System (CIS). For example, they are retained after a person dies or moves abroad. This is because individuals who move abroad may at some point have a call upon contributions paid whilst in the UK. In the case of deceased individuals, a partner may make a claim for a contributory benefit, which is dependent on the contribution record of the deceased individual. This means that the number of accounts held on the system accrues as NINOs are allocated each year.

A joint data cleansing exercise was carried out in 2000-01 with Her Majesty's Revenue and Customs, who jointly own the NINO. This exercise identified NINOs for which there had been no activity for a considerable period of time and which were not known to the National Insurance Recording System (NIRs). This exercise removed 200,000 NINOs from DCI.