National Insurance numbers

National Insurance number

The National Insurance numbercard issued by the former Department of Health and Social Security to Zacarias Moussaoui

People born and resident in the UK are assigned an NI number (referred to internally as a NINO), and receive a plastic 'numbercard' of similar proportions to a credit card with the number raised on the front shortly before their 16th birthday, and are advised to keep the card safe (only one replacement card may ever be issued over the lifetime of an individual). However, allocation of this number might occur a long time before this occasion (the date can usually be established from the prefix letters used), and siblings may have consecutive numbers - this is dependent on the payment of Child Benefit.
Persons from abroad who wish to work in the UK, or those to whom a number was not initially allocated as children, may apply for a number through the Department for Work and Pensions (DWP). The prefixes used are typically different from those used in the normal run.
The format of the number is two letters, six digits, and one further letter or a space. The example used is typically AB123456C. It is usual to pair off the digits - such separators are seen on forms used by government departments (both internal and external, notably the P45 and P60).
In the case of AB 12 34 56 C, the first and second letter cannot be D, F, I, Q, U or V. The second letter also cannot be O. The first two character combinations BG, GB, NK, KN, TN, NT and ZZ are not used. The six digits are sequentially issued (siblings who are few years apart may notice their numbers are consecutive when the numbers are issued together), and the suffix letter is A, B, C, D or absent. The number is unique without the last letter - if there is AB 12 34 56 C, then there will be no AB 12 34 56 D (though it is possible that there will be AB 12 34 57 D). A common error found on documents containing an individual's NI number is the final letter being incorrect; however, an individual still can be identified without that last letter.
Historically, the suffixes A, B, C and D at the end of the National Insurance (NI) number indicated the period of validity of the NI cards originally used to collect contributions. Cards were exchanged every twelve months and because of the very large numbers of cards issued the exchange was staggered. Suffix A cards ran from March of one year until March of the next when they were exchanged for a new one. Stagger B suffix cards ran from June until June, stagger C from September until September and stagger D from December until December. For example a B stagger card YA472359B may have run from the first Monday in June 1955 until the first Sunday in June 1956. This system operated from 5 July 1948 until April 1975 (when the A stagger cards were extended to run an extra 5 weeks until April 5th in line with the start of the tax year which then became the period of validity for contributions collected under the new computerised system which took over from April 1975). Expired NI cards were sorted into one hundred separate groups corresponding to the final two numbers of the NI number and were posted to the individual insured person's NI account (the RF1) by the corresponding one hundred ledger sections at the Records Branch of the Central Office of the Ministry of Pensions and National Insurance and its later incarnations - MOSS, DHSS, DSS, Contributions Agency, etc. These 100 sections dealt not only with the recording of NI contributions but with requests for information about qualifying contributions necessary to pay sickness, unemployment, widows and other benefits and also with any correspondence arising from those NI accounts and NI cards. Within each of the 100 sections, NI numbers were divided into 16 further 'splits', where any NI cards and correspondence for NI numbers within those splits would be dealt with by one clerk. When an NI number was not known or incorrect the NI card would go to General Index where millions of small index slips (the RF2) were filed in alphabetical order of surname and showed the surname(s), first names, date of birth and NI number for every person within the National Insurance scheme. Thus an illegible, wrong or missing NI number could be traced with reference to these index slips using the person's name and date of birth. Northern Ireland had a similar system to that described in this paragraph.
National Insurance numbers issued in the Isle of Man hold the prefix 'MA'. Similarly, those issued in Jersey start with 'JY', and those issued in Guernsey hold the prefix 'GY'.
An individual's NI number can never change, although they may be issued with a second NI number when all traces of their original number have been lost. Some accountants often mistakenly advise their customers of a change, particularly in the suffix letter, where A referred to employment, B to self-employment, etc. The actual meaning of the suffix letter dates back to before NIRS, as explained above.
As the UK does not have a system of personal ID cards, and not everyone has a passport, the NI number is, along with the NHS number, one of only two systems which provide every adult in the country with a code number. Consequently, NI numbers are sometimes used for identification purposes in other contexts which have nothing to do with their original National Insurance purpose. The NI card, however, is not proof of identity.
In the past, employers sometimes allocated their employees a temporary insurance number, which followed the format TN 01 23 45 X, where 'TN' stands for temporary number and is static and X is usually M for male or F for female and the numbers in the mid-section are the employee's date of birth. In the case of a woman born on 1 December 1958, for example, the temporary NI number would most likely be TN 01 12 58 F. This has now changed slightly in that the TN prefix is no longer used. Temporary NI numbers cannot be used to trace back any NI credits or personal details. HMRC now discourages the use of these numbers.
Another type of temporary NI number is the Revenue-issued "temporary reference" used when HMRC is unable to trace a taxpayer's original NI number. It follows the format 63T12345.