This is an HTML version of an attachment to the Freedom of Information request 'National Insurance number format'.

 
 
 
DWP Central Freedom of Information Team
Annex A 
 
e-mail: xxxxxxxxxxxxxxxxxxxxxxxxxxxxxx@xxx.xxx.  
gov.uk
 
Our Ref: VTR 4543
 
 

11 October 2013
Annex A 
 
 
 
 
 
 
 
Dear Mr Hilton,  
 
Thank you for your Freedom of Information request received on 23rd September 2013.   You 
asked:- 
 
I understand that the National Insurance Number (NINO) is in the format "AA NN NN NN A", 
where A represents a letter and N a number from 0–9. 
 
Could you please provide the following information under the Freedom of Information Act: 
 
1. A list of the two-letter combinations ever used as the first two characters of NINOs so far 
issued to people in the UK. 
 
2. A list of the two-letter combinations ever used as the first two characters of NINOs used for 
administrative or other special reasons (e.g. "TN", "MW", "PP"). 
 
3. A list of the two-letter combinations scheduled to be used as the first two characters of 
future NINOs for people in the UK. 
 
4. A list of the two-letter combinations scheduled to be used as the first two characters of 
future NINOs for administrative or other special reasons. 
 
5. A list of letters ever used as the final (9th) character of NINOs. 
 
6. The reasons why "GB", "BG", "NK", "KN", "NT", and "ZZ" cannot be used as the first two 
characters of a NINO. 
 
7. The reasons why "F", "M", and "P" were used as the final (9th) character of NINOs. 
 
Could you also answer the following questions: 
 


1. Is it true that the numbers (the 3rd–8th characters) of NINOs are allocated consecutively 
from "000000" to "999999"? (And if not, how are they allocated? And from what starting 
number does the allocation begin? And at which number does it end?) 
 
2. Do any of the characters of NINOs act as a "check digit" by which the validity of the NINO 
can be verified (using the otherz constituent characters of the NINO)? 

DWP Response
I can confirm that the format of the National Insurance number (NINo) is as you have 
described above. 
With regard to questions 1 and 3: 
1. A list of the two-letter combinations ever used as the first two characters of NINOs so far 
issued to people in the UK. 
3. A list of the two-letter combinations scheduled to be used as the first two characters of 
future NINOs for people in the UK.
 
 
The list of the two letter combinations used and scheduled to be used are detailed below. This 
information is provided by Her Majesty’s Revenue and Customs (HMRC) to assist employers 
in administrating payroll. It is available in the “Quality Standard and Business Validation 
Specification From April 2011” on the HMRC website: 
http://www.hmrc.gov.uk/ebu/qual_stand_11.pdf 
 
 
National Insurance Number Prefixes  
 
AA, AB, AE, AH, AK, AL, AM, AP, AR, AS, AT, AW, AX, AY, AZ  
BA, BB, BE, BH, BK, BL, BM, BT  
CA, CB, CE, CH, CK, CL, CR  
EA, EB, EE, EH, EK, EL, EM, EP, ER, ES, ET, EW, EX, EY, EZ  
GY  
HA, HB, HE, HH, HK, HL, HM, HP, HR, HS, HT, HW, HX, HY, HZ  
JA, JB, JC, JE, JG, JH, JJ, JK, JL, JM, JN, JP, JR, JS, JT, JW, JX, JY, JZ  
KA, KB, KE, KH, KK, KL, KM, KP, KR, KS, KT, KW, KX, KY, KZ  
LA, LB, LE, LH, LK, LL, LM, LP, LR, LS, LT, LW, LX, LY, LZ  
MA, MW, MX  
NA, NB, NE, NH, NL, NM, NP, NR, NS, NW, NX, NY, NZ  
OA, OB, OE, OH, OK, OL, OM, OP, OR, OS, OX  
PA, PB, PC, PE, PG, PH, PJ, PK, PL, PM, PN, PP, PR, PS, PT, PW, PX, PY  
RA, RB, RE, RH, RK, RM, RP, RR, RS, RT, RW, RX, RY, RZ  
SA, SB, SC, SE, SG, SH, SJ, SK, SL, SM, SN, SP, SR, SS, ST, SW, SX, SY, SZ  
TA, TB, TE, TH, TK, TL, TM, TP, TR, TS, TT, TW, TX, TY, TZ  
WA, WB, WE, WK, WL, WM, WP  
YA, YB, YE, YH, YK, YL, YM, YP, YR, YS, YT, YW, YX, YY, YZ  
ZA, ZB, ZE, ZH, ZK, ZL, ZM, ZP, ZR, ZS, ZT, ZW, ZX, ZY  
 
The characters D, F, I, Q, U and V are not used as either the first or second letter of a NINO 
prefix. 
 

 
 
 
With regard to questions 2, 4 and 7: 
2: A list of the two-letter combinations ever used as the first two characters of NINOs used for 
administrative or other special reasons (e.g. "TN", "MW", "PP"). 
4.A list of two-letter combinations scheduled to be used as the first two characters of future 
NINos for administrative or other special reasons. 
7. The reasons why "F", "M", and "P" were used as the final (9th) character of NINOs. 
 
A temporary or administrative number is not a NINo. Historically, when employers or Pension 
Providers did not know and employee’s or pensioner’s NINo they used to construct a number 
usually starting with TN (temporary number) the individual’s date of birth followed by gender 
M/F (or P for pensioner) for example TN010160M. This was not a unique identifier as two 
individuals with the same date of birth and gender would have the same temporary 
administrative number. Employers were instructed to cease this practice from April 2001.  
Further details of the use of temporary reference or administrative numbers can be found at 
the HMRC website: http://www.hmrc.gov.uk/manuals/nimmanual/nim39110.htm 
 
There is no intention to use any other first two characters for temporary or administrative 
reference numbers.  
 
6. The reasons why "GB", "BG", "NK", "KN", "NT", and "ZZ" cannot be used as the first two 
characters of a NINO. 

These prefixes are not used because of risks of confusion or error.   
1. Is it true that the numbers (the 3rd–8th characters) of NINOs are allocated consecutively 
from "000000" to "999999"? (And if not, how are they allocated? And from what starting 
number does the allocation begin? And at which number does it end?) 

Yes it is correct that the NINo is allocated consecutively 000000 – 999999. 
2. Do any of the characters of NINOs act as a "check digit" by which the validity of the NINO 
can be verified (using the otherz constituent characters of the NINO)? 

There are no characters of the NINo that act as a check digit. 
If you have any queries about this letter please contact me quoting the reference number 
above.   
Yours sincerely,  
 
 
DWP Central FoI Team 
 
 
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If you are not happy with this response you may request an internal review by e-mailing freedom-of-information-
xxxxxxx@xxx.xxx.xxx.xx or by writing to DWP, Central FoI Team, Caxton House, Tothill Street, London, SW1H 
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