National Insurance Number

Detects National Insurance Number patterns. This pattern is based on a Microsoft Purview built-in sensitive information type. Users already running Purview may prefer to enable the built-in SIT directly, or use this version as a starting point for customisation.

Type: regex
Engine: universal
Confidence: medium
Confidence justification: Medium confidence: pattern has structural constraints but corroborative keywords are recommended to reduce false positive rates.
Detection quality: Verified
Jurisdictions: uk
Frameworks: ISO 27001, ISO 27701
Data categories: pii, government-id
Scope: narrow
Risk rating: 9
Platform compatibility: Purview: Compatible, GCP DLP: Unsupported, Macie: Unsupported, Zscaler: Compatible, Palo Alto: Unsupported, Netskope: Unsupported

Pattern

\b(?!BG|GB|NK|KN|TN|NT|ZZ)[A-CEGHJ-PR-TW-Z][A-CEGHJ-NPR-TW-Z]\s?\d{2}\s?\d{2}\s?\d{2}\s?[A-D]\b

Corroborative evidence keywords

identifier, number, ID, ID number, identification, ID card, license, permit, registration, certificate

Proximity: 300 characters

Should match

AB 12 34 56 A — Spaced NINO format
AB123456A — Compact NINO format
CE 12 34 56 B — Alternate prefix NINO

Should not match

BG 12 34 56 A — Invalid prefix (BG is an excluded combination)
AB 12 34 56 E — Invalid suffix letter (E not in A-D range)
AB 12 34 56 — Missing suffix letter

Known false positives

Common words and phrases related to national insurance number appearing in policy documents, training materials, HR templates, or compliance guidelines without actual personal data. Mitigation: Require corroborative evidence keywords within the proximity window to confirm sensitive data context rather than general discussion.
In British English, similar terminology used in formal or administrative contexts (education, professional documentation) that does not constitute sensitive data collection. Mitigation: Layer with additional contextual signals such as structured identifiers, form fields, or database column headers to distinguish sensitive records from general references.

References

U.K. national insurance number (NINO) entity definition - Microsoft Learn