UK National Insurance Number Regex for Go

What this pattern does

This page provides a comprehensive, battle-tested regular expression for matching uk national insurance number, ported and verified for Go. Financial data validation has zero tolerance for false negatives — a missed invalid entry can corrupt downstream calculations. The snippet below is ready to drop into your Go project — whether you're validating in a Gin handler, a gRPC service, or a command-line tool.

Go Implementation

// UK National Insurance Number
// ReDoS-safe | RegexVault — Finance > Tax & Registration

package validation

import "regexp"

var ukNationalInsuranceNumberRe = regexp.MustCompile(`^(?:QQ|(?!BG|GB|NK|KN|TN|NT|ZZ)[A-CEGHJ-NOPR-TW-Z]{1}[A-CEGHJ-NPR-TW-Z]{1})[0-9]{6}[A-D]$`)

func ValidateUkNationalInsuranceNumber(s string) bool {
    return ukNationalInsuranceNumberRe.MatchString(s)
}

// Example
// fmt.Println(ValidateUkNationalInsuranceNumber("AB123456C")) // true

Test Cases

When to use this pattern

This pattern is drawn from the Finance > Tax & Registration category and carries a ReDoS-safe certification. That matters for Go developers because Go's RE2 engine is inherently safe from catastrophic backtracking, but this pattern has been additionally verified for correctness. RegexVault audits patterns against known backtracking attack vectors, ensuring you have the necessary context before using this regex in a high-stakes production environment.

Common Pitfalls

Technical Notes

Invalid prefixes: BG, GB, NK, KN, TN, NT, ZZ. Second letter excludes D, F, I, Q, U, V. First letter also excludes D, F, I, Q, U, V plus O. Suffix must be A-D (not E onward).