UK NINO Generator

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NINO format and invalid prefixes

NINO format: letters and prefixes that are never used

A NINO looks simple, but it has rules that reject most invented numbers: banned letters, reserved prefixes and a restricted suffix. This page sums up what the HMRC manual says and opens the tool ready to generate and validate.

The rules, one by one

According to the National Insurance Manual (NIM39110), a NINO has 2 letters, 6 digits and a final letter that is always A, B, C or D. The letters D, F, I, Q, U and V never appear as the first or second letter of the prefix, and O is never the second letter. On top of that, the prefixes BG, GB, KN, NK, NT, TN and ZZ are not to be used.
The manual also mentions administrative or temporary prefixes such as OO (tax credits where no NINO exists), FY, NC, PP and PZ, which do not identify a person. And it shows QQ 12 34 56 A as an example only: because Q is never valid, QQ numbers can never be real, which makes them ideal for documentation. None of this proves a NINO was issued, because there is no check digit.

Examples in the validator

Manual example

Input: QQ 12 34 56 A
Expected output: Reprovado: primeira e segunda letra (Q)

It is a documentation example only; Q is never used in the prefix.

Unassigned prefix

Input: BG 12 34 56 A
Expected output: Reprovado: prefixo BG não é usado

The letters are allowed, but the BG combination is on the HMRC list.

Full tool FAQ

What does a NINO look like?

Two letters, six digits and a final letter, written like QQ 12 34 56 C. The final letter is always A, B, C or D, a leftover from the old quarterly contribution cards.

Which letters are never used?

Which prefixes are not allocated?

What is QQ 12 34 56 A?

Can a generated number belong to a real person?

Does the validator confirm a NINO exists?

What is a temporary reference number?

Is it safe to use generated numbers in production?

Frequently asked questions

Which number should I use in docs and demos?

Use Safe test mode: it only generates prefixes HMRC documents as never assigned (QQ and the unused prefixes), with no risk of landing on a real person.

Why is a NINO with suffix E invalid?

The suffix is always A, B, C or D, a leftover from the old quarterly cards. Any other letter fails the suffix rule.

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NINO format and invalid prefixes

NINO format: letters and prefixes that are never used

The rules, one by one

According to the National Insurance Manual (NIM39110), a NINO has 2 letters, 6 digits and a final letter that is always A, B, C or D. The letters D, F, I, Q, U and V never appear as the first or second letter of the prefix, and O is never the second letter. On top of that, the prefixes BG, GB, KN, NK, NT, TN and ZZ are not to be used.

The manual also mentions administrative or temporary prefixes such as OO (tax credits where no NINO exists), FY, NC, PP and PZ, which do not identify a person. And it shows QQ 12 34 56 A as an example only: because Q is never valid, QQ numbers can never be real, which makes them ideal for documentation. None of this proves a NINO was issued, because there is no check digit.

Examples in the validator

Manual example

Input: QQ 12 34 56 A
Expected output: Reprovado: primeira e segunda letra (Q)

It is a documentation example only; Q is never used in the prefix.

Unassigned prefix

Input: BG 12 34 56 A
Expected output: Reprovado: prefixo BG não é usado

The letters are allowed, but the BG combination is on the HMRC list.

Full tool FAQ

What does a NINO look like?

Two letters, six digits and a final letter, written like QQ 12 34 56 C. The final letter is always A, B, C or D, a leftover from the old quarterly contribution cards.

Which letters are never used?

Which prefixes are not allocated?

What is QQ 12 34 56 A?

Can a generated number belong to a real person?

Does the validator confirm a NINO exists?

What is a temporary reference number?

Is it safe to use generated numbers in production?

Frequently asked questions

Which number should I use in docs and demos?

Use Safe test mode: it only generates prefixes HMRC documents as never assigned (QQ and the unused prefixes), with no risk of landing on a real person.

Why is a NINO with suffix E invalid?

The suffix is always A, B, C or D, a leftover from the old quarterly cards. Any other letter fails the suffix rule.