International · Validation
UK National Insurance Number validator.
Check a NINO's shape against HMRC's own published prefix and suffix rules — which letters can never start a prefix, which pairs are never issued, and which final letter is allowed.
Important, up front: unlike a SIN or a VIN, HMRC has never published a check digit for a NINO. It is an assigned identifier, not a self-checking one. This tool validates the documented format rules — it cannot confirm a number was ever actually issued.
Inputs
Result
Enter a National Insurance Number and press Check.
How a NINO is structured
A National Insurance Number is a nine-character identifier: a two-letter prefix, six digits, and a final suffix letter (for example AB 12 34 56 C). HMRC's own National Insurance Manual (NIM39110) documents exactly which letters and pairs are never used, rather than leaving it to guesswork:
| Rule | Detail |
|---|---|
| Banned from either prefix letter | D, F, I, Q, U, V |
| Banned from the second prefix letter only | O |
| Prefix pairs never issued | BG, GB, KN, NK, NT, TN, ZZ |
| Valid final (suffix) letters | A, B, C, D |
HMRC's own illustrative example in that manual, QQ 12 34 56 A, is explicitly a placeholder and not a real prefix — it starts with Q, which the same rules ban outright. This tool correctly reports that example as invalid, exactly as HMRC intends.
No checksum exists on a NINO
A Social Insurance Number and a VIN both carry a real, published check digit that lets you catch a typo mathematically. A NINO does not: it is simply an assigned identifier with no self-check digit built in. That means this tool can tell you a NINO is the right shape, but it cannot tell you whether a specific number was ever actually issued to a real person — only HMRC can do that.
Format check only — not an HMRC lookup
This tool checks format entirely in your browser against HMRC's published rules. It does not query HMRC, and a shape-valid result is not proof the number was ever issued. Nothing you type is transmitted, stored, or logged.