Meaning of Last Letter of UK National Insurance Number

Updated on April 5, 2018
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I write about employment issues, ways to earn money and how to get best value when spending it.

Every British worker has a unique National Insurance (NI) number.
Every British worker has a unique National Insurance (NI) number. | Source

NI Number Stands in for a UK Identity Card

The United Kingdom has no formal identity card or document. In most cases a person’s passport is the document used to prove their identity. As recently as 2010, there was an attempt by the UK government to introduce compulsory ID cards, but the idea was very unpopular. The government eventually dropped the scheme because of protests about such documents becoming an unnecessary invasion of privacy.

However most people living in Britain are already on a national database without realising it. Once you are aged over sixteen years and start paid work in the United Kingdom you are automatically issued with a National Insurance (NI) number. A person’s NI number is very important as it is used to link employment records with social security benefits and tax payment records.

What is NINO? Who Pays National Insurance?

National Insurance Payments

National Insurance is paid by everyone working in the UK who earns over a certain amount. The contributions are recorded centrally and they determine eligibility for all health and social security benefits including the State Pension.

For the tax year 2016-17, the threshold for making a contribution was £155 per week.

In 2017-18 the minimum threshold for starting to pay national insurance was reduced to £113 per week. i.e. more people on low wages will have to pay NI contributions. Some people say this is a way of indirectly increasing the tax burden on everyone who is employed.

Do you know your National Insurance number off by heart?

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Meaning of NI Number and Letter Combination

Your National Insurance number may look like a random string of numbers and letters. Each person is issued with a unique number and letter combination. This number is individual to you and remains the same whether you move house or get married. The number is your personal identifier and remains the same throughout your life.

An NI (National Insurance) number consists of three parts. The first two letters are known as the prefix letters. These are followed by six numerals. Finally, there is a single suffix letter at the end of the string.

Unique British National Insurance Number

Fictitious example
Prefix letters
originally linked to location
Middle numbers
random sequence
Suffix letter
shows season for audit
A 1940's British National Insurance card (from before the days of computers.) Each stamp on the card is proof of a week's paid NI contribution.
A 1940's British National Insurance card (from before the days of computers.) Each stamp on the card is proof of a week's paid NI contribution. | Source

Prefix Letters

When the system first started, the two prefix letters (at the beginning) were intended to represent the geographical location of the individual holding that National Insurance identity. However, the system was flawed because some areas of the country were more populous than others. Thus the number of unique combinations using the same two prefix letters was used up more quickly in some areas. So the system was changed.

The NI prefix letters that are currently used are not randomly generated. There is no publicly available information on how these new number combinations are created. The UK government uses the Freedom of information Act 2000 to withhold details of how exactly the numbers are chosen.

Middle Random Number Sequence

The six numbers contained within each unique National Insurance number are a random sequence of numerals. These middle numbers are used by government departments like HMRC (Her Majesty’s Revenue and Customs) and the DWP (Department of Work and Pensions) as a unique identifier for each person. These, used in tandem with the prefix and suffix letters, give an individual identity number to every working person in the UK.

Suffix Letter

The lone suffix letter (at the end) is a leftover identifier which relates to the manual collection of national insurance payments. Pre electronic record-keeping, a physical record of National Insurance payments was kept. Every employer had to literally buy a physical stamp and stick it onto a National Insurance card. There was one of these NI cards kept for each employee. The stamp proved that an employer had paid the appropriate NI contribution for that particular employee for that week.

There were millions of these cards and they needed to be checked annually by the government. In order for the checking to be spread evenly over each twelve month period, every NI card was linked to a particular month. This was signified by the suffix letter at the end of the National Insurance number. This ensured that during each three-month period, only one quarter of the nation’s National Insurance cards were being processed by the relevant government department.

For example, a card which had a suffix letter "A" would be sent for checking at the beginning of March.

The letter "B" was the designation for cards to be examined at the beginning of June.

The letter "C" showed that the card should be ready for inspection at the start of September.

The suffix "D" was for the final quarter of the year and was for cards to be checked in December each year.

With electronic processing and instant transfer of payments, the suffix letter of the U.K.’s National Insurance number has become irrelevant. However, it is still necessary to use it, as without the full unique combination, your National Insurance number will not be accepted as valid.

In the UK, it is compulsory to make National insurance contributions. The more you earn, the higher NI you pay.
In the UK, it is compulsory to make National insurance contributions. The more you earn, the higher NI you pay. | Source

Non-UK Passport Holders and National Insurance

Non-UK passport holders will not be issued with a National Insurance number unless they are resident in the UK for study or work purposes and hold an appropriate study or work visa.

It is not possible to get a UK National Insurance number if you are only on vacation in the UK. It is illegal to obtain work in the UK without the relevant visa documents and work permit.

How to Apply For Your NI Number

Does the UK Use the Suffix Letter On New NI Numbers?

Yes. A suffix letter is an integral part of all UK National Insurance (NI) numbers. There was an instance some years ago where a batch of numbers were mistakenly issued with the last letter missing. The issue of new numbers was temporarily put on hold, as fraud was suspected. This is now resolved, and you should contact HMRC if you think your National Insurance number is incorrect.

All legitimate NI numbers are made up of a two-letter prefix, followed by six numbers, and then a single letter suffix.

Past, Present and Future of National Insurance

More Information From HMRC

For accurate and up-to-date information about applying for a UK National Insurance and current contribution levels, you should refer to Her Majesty's Revenue and Customs (HMRC) website.


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