UK National Insurance number: two letters from the allowed set, six digits, then a letter from A to D. The prefix classes exclude D, F, I, Q, U and V, which HMRC never issues, so the shape alone is already selective. One consequence worth knowing: HMRC's own example number QQ123456C is not matched, because Q is one of the excluded letters, which is exactly why HMRC publishes it.
Label: UK_NINO
\b[A-CEGHJ-PR-TW-Z]{2}\d{6}[A-D]\bNI number AB123456C on the payslip. → AB123456CReference AB654321A recorded. → AB654321ADA123456CQQ123456CAB123456ZTags: uk, government-id, identity, hr