NINo UK National Insurance Validator

What is a UK National Insurance Number?

The National Insurance Number (NINo) is the UK's unique identifier for the National Insurance and tax systems, administered by HMRC and the DWP. It tracks the contributions and benefits tied to each individual.

Its format is two prefix letters + six digits + one suffix letter, for example QQ 12 34 56 C. QQ123456C is the official placeholder used in examples.

Format rules

Validation is purely about the letters and shape — there is no arithmetic checksum:

• The first and second letters cannot be D, F, I, Q, U or V.
• The second letter additionally cannot be O.
• Disallowed prefixes include BG, GB, NK, KN, TN, NT and ZZ.
• The suffix letter must be A, B, C or D.

Why there is no checksum

Unlike many national IDs, the NINo's six digits are essentially a serial number with no built-in check digit. Validation therefore only confirms that the letters and positions follow the rules — it cannot prove the number was actually issued to someone.

Common pitfalls

• Allowing forbidden letters such as D, F, I, Q, U or V in the prefix.
• Accepting a suffix outside A-D (for instance E or a digit).
• Forgetting that some two-letter combinations like BG or ZZ are reserved and never issued.
• Expecting a checksum to catch typos — there isn't one, so the six digits cannot be self-verified.

FAQ

Does the NINo have a check digit? No. Validation is limited to the letter and format rules; the digits carry no checksum.

Is QQ123456C a real number? No. It is the standard placeholder used in documentation and forms, never a genuine allocation.

Why are spaces shown in the number? The grouped form QQ 12 34 56 C is only for readability — strip spaces before validating.