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HMRC internal manual

National Insurance Manual

National Insurance Numbers (NINOs): Format and Security: What a NINO looks like

A NINO is made up of two letters, six numbers and a final letter, which is always A, B, C, or D.

It looks something like this:

QQ 12 34 56 A

This is an example only and should not be used as an actual number.

The Prefix

A prefix is chosen and then used until all the possible numbers have been allocated. Then another prefix is used but not necessarily the next one alphabetically. The characters D, F, I, Q, U and V are not used as either the first or second letter of a NINO prefix. The letter O is not used as the second letter of a prefix. (This content has been withheld because of exemptions in the Freedom of Information Act 2000) NIM39115(This content has been withheld because of exemptions in the Freedom of Information Act 2000)  

The Suffix

The suffix dates back to when contributions were recorded on cards which were returned annually, staggered throughout the tax year. “A” meant the card was to be returned in March; “B” in June; “C” in September and “D” in December. Although contribution cards are no longer used, the suffix has remained an integral part of the NINO.

Administrative Numbers

For administrative reasons it has sometimes been necessary for HMRC and DWP to use reference numbers which look like NINOs but which do not use valid prefixes. The administrative prefixes used are:


This “prefix” is used for administering Tax Credits where no NINO is held at the start of the tax credit claim. The customer should already have applied for a valid UK NINO.


Is issued exclusively by Account Investigations section (AIS) in NIC&EO


Previously used for Attendance Allowance claims


Used between January 1980 and January 1987 for Migrant Workers, MW is not a valid prefix.


For Stakeholder Pensions, a scheme administrator may need to allocate a dummy identifier beginning ‘NC’ followed by six numbers based on the date of birth and ending with ‘m’ or ‘f’ for the gender. This dummy identifier should only be used for personal pension end of year reporting, and the member must not be given the dummy identifier. This reference number is used by the HMRC for personal pension compliance data matching only as it is not a verified prefix and is not held on our systems, it will not be accepted by the Quality Standard for end of year filing from 2005-2006.


The PP999999P temporary NINO may be “allocated” by pension schemes for the purpose of HMRC reporting. The PP prefix will continue to be accepted by the Quality Standard. However, it is not a valid NINO for National Insurance purposes so employers should not use it for NIC payroll purposes.


HMRC have used PZ and PY as administrative numbers since the 1970’s for tax only cases but have not created any new numbers since August 2002. They are not valid National Insurance Number prefixes and will not be accepted by the Quality Standard. NICs cannot be posted against a PZ number as it is not set up as a full National Insurance Account. Anyone with a PZ or PY number who is liable or wishes to pay NICs must apply for a valid NINO. From 2004-2005, if an employer tries to use a PZ on an end of year return, it will fail the Quality Standard. If an employer only has a PZ or PY number for an employee, they should follow the instructions in Employers Guides, or on the HMRC internet site and enter the employee’s date of birth and gender on the forms. See NIM39210.


These are Temporary Numbers which were used by employers and DWP when they did not know an individual’s NINO.

Employers are no longer permitted to use TN numbers and they will not be accepted by the Quality Standard. If the employer does not know an employee’s NINO when they submit their end of year return, they should leave the NINO box blank, enter the employee’s date of birth and gender in the appropriate boxes on the form, following the guidance in Employers’ Guidance, or on the HMRC internet site. See NIM39210.