regex101: National Insurance Number regular expression

^start of line

Negative Lookahead(?!BG|GB|KN|NK|NT|TN|ZZ)

1st AlternativeBG

BGthe literal text BG (case insensitive)

2nd AlternativeGB

GBthe literal text GB (case insensitive)

3rd AlternativeKN

KNthe literal text KN (case insensitive)

4th AlternativeNK

NKthe literal text NK (case insensitive)

5th AlternativeNT

NTthe literal text NT (case insensitive)

6th AlternativeTN

TNthe literal text TN (case insensitive)

7th AlternativeZZ

ZZthe literal text ZZ (case insensitive)

Negated Character Class[^DFIQUV]

Dthe literal D (68₁₀ / 104₈ / 44₁₆) (case insensitive)

Fthe literal F (70₁₀ / 106₈ / 46₁₆) (case insensitive)

Ithe literal I (73₁₀ / 111₈ / 49₁₆) (case insensitive)

Qthe literal Q (81₁₀ / 121₈ / 51₁₆) (case insensitive)

Uthe literal U (85₁₀ / 125₈ / 55₁₆) (case insensitive)

Vthe literal V (86₁₀ / 126₈ / 56₁₆) (case insensitive)

Negated Character Class[^DFIQUVo]

Dthe literal D (68₁₀ / 104₈ / 44₁₆) (case insensitive)

Fthe literal F (70₁₀ / 106₈ / 46₁₆) (case insensitive)

Ithe literal I (73₁₀ / 111₈ / 49₁₆) (case insensitive)

Qthe literal Q (81₁₀ / 121₈ / 51₁₆) (case insensitive)

Uthe literal U (85₁₀ / 125₈ / 55₁₆) (case insensitive)

Vthe literal V (86₁₀ / 126₈ / 56₁₆) (case insensitive)

othe literal o (111₁₀ / 157₈ / 6F₁₆) (case insensitive)

Character Class[0-9]{6}

{6}matches exactly 6 characters from the set below:

0-9one character from 0 (48₁₀) to 9 (57₁₀)

Character Class[ABCD]

Athe literal A (65₁₀ / 101₈ / 41₁₆) (case insensitive)

Bthe literal B (66₁₀ / 102₈ / 42₁₆) (case insensitive)

Cthe literal C (67₁₀ / 103₈ / 43₁₆) (case insensitive)

Dthe literal D (68₁₀ / 104₈ / 44₁₆) (case insensitive)

$end of line

Global pattern flags

i modifier: insensitive. Matches without distinguishing uppercase and lowercase letters

m modifier: multiline. Causes ^ and $ to match the start and end of each line, not only the start and end of the string

g modifier: global. Finds all matches instead of stopping after the first

25 tokens

Regular Expression

^(?!BG|GB|KN|NK|NT|TN|ZZ)[^DFIQUV][^DFIQUVo][0-9]{6}[ABCD]$

New

BG283902A
AD283902A
AO283902A
AA283902Z
AA283902A

BG283902A
AD283902A
AO283902A
AA283902Z
AA283902A