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Freedom of Information request NIC-690159-K8H4Z

Freedom of information request to provide more information about the format of NHS numbers and to request a guide/reference or index to these number structures. 

I understand that the format of NHS numbers has varied over time, and that each format was probably in force for a specific period.

Do you hold a guide / reference / index to these differing number structures and the periods that they applied to?”

We have considered your request and in accordance with S.1 (1) of the Freedom of Information Act 2000 (FOIA) I can confirm that we do hold the information that you have requested.

NHS Digital has no specific guidance about NHS Number formats prior to the introduction of the current 10 digit NHS Number in 1995/1996, in order to facilitate the implementation of the electronic health record. Over 20 different formats of NHS Number were in use prior to 1995 which made accurate validation of records very difficult and necessitated the introduction of a new single unique identifier.

"New NHS numbers" were allocated to every new-born from July 1995, generally introduced in 1996, and became mandatory on 1 April 1999. This replaced the previous system founded on wartime identity card numbers, which in England and Wales used letters and digits (e.g. JRDAN 269); The numerical part of ID/NHS numbers allocated to people born after the Second World War in England and Wales matched the birth register entry number (i.e. a person whose birth was entry number xy would have an ID/NHS number in the format LLLLxy). The letters contained within the ID/NHS Number, related to the area of England or the office allocating the number. Between 1969 and July 1995, the old-style NHS number was used on a baby's birth certificate as the reference number for the certificate.

The NHS number was developed to support unique patient identification within the NHS. It is a unique 10-digit number. The first nine digits are the identifier and the tenth is a check digit used to confirm the number's validity. There is no significance to any of the digits.. This style of numbering was introduced in 1996 replacing a variety of previous systems. The NHS number should be displayed and printed in a '3 3 4' format (e.g. 943 476 5919). The National Patient Safety Agency (NPSA) published a Safer Practice Notice (SPN) for the NHS number in September 2008 which advised all NHS organisations to use the NHS number as the national patient identifier.

The NHS number is now widely used within health and social care organisations and should be present on all patient and service user records, both paper and electronic, as early in the care pathway as possible. It must be used alongside other demographic information to link together the correct records for a particular patient or service user.

The current 10-digit NHS Number, is made up of 9 digits with the tenth digit being a checksum.

The checksum is calculated by multiplying each of the first nine digits by 11 minus its position. Using the number 943 476 5919 as an example

  • the first digit is 9. This is multiplied by 10
  • the second digit is 4. This is multiplied by 9
  • and so on until the ninth digit (1) is multiplied by 2
  • the result of this calculation is summed. In this example: 9*10+4*9+3*8+4*7+7*6+6*5+5*4+9*3+1*2 = 299
  • the remainder when dividing this number by 11 is calculated, yielding a number in the range 0–10, which would be 2 in this case
  • finally, this number is subtracted from 11 to give the checksum in the range 1–11, in this case 9, which becomes the last digit of the NHS number
  • a checksum of 11 is represented by 0 in the final NHS number. If the checksum is 10 then the number is not valid

All people registered for primary care will have a valid NHS Number and record on PDS.

Very few people resident within England and Wales will not have an NHS Number and PDS record.

NHS Numbers are never re-used and are issued / allocated from the following ranges.

000-000-001 to 009-999-999 Unreserved (not in use)
010-000-000 to 311-299-999 Not to be issued (Scotland CHI numbers)
311-300-000 to 319-999-999


320-000-000 to 399-999-999 Northern Ireland
400-000-000 to 499-999-999

England Wales and IOM

500-000-000 to 599-999-999 Not to be issued
600-000-000 to 799-999-999 England Wales and IOM
800-000-000 to 859-999-999 Reserved for possible future use by Republic of Ireland
860-000-000 to 899-999-999 Unreserved
900-000-000 to 999-999-999

Not to be issued (Synthetic/test patients PDS) 

Currently all NHS Numbers in use are from the 4, 6 and 7 ranges with a few from the 3 range where patients from Northern Ireland have registered for primary care in England and the NHS Numbers have been added to Personal Demographics Service (PDS).

Last edited: 17 January 2023 1:04 pm