NHS number

NHS numbers are the unique numbers allocated to registered users of the three public health services in England, Wales and the Isle of Man; the three health systems use a shared numbering scheme. It is the key to the implementation of the electronic health record, and is to be incorporated in all new software deployed within the National Health Service (NHS).
History.
The modern style of NHS number was generally introduced in 1996, although they were allocated to every new-born from July 1995, before becoming mandatory on 1 April 1997. It replaced the previous system founded on wartime identity card numbers, which in England and Wales used letters and digits (e.g. JRDAN 269); Scotland used numbers based on households with individuals further identified within the household (e.g. STUV123:3), and this meant that it was hard to validate a specific number. 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). 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.
Format.
The current system uses a ten-digit number in '3 3 4' format with the final digit being an error-detecting checksum. Examples given include 987 654 4321.
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:
A person gets an NHS number at birth, or when they first make contact with the NHS by registering with a GP. It comes from a record being made on the Personal Demographics Service, a national patient database. NHS Numbers are re-issued if a patient is adopted or undergoes gender re-assignment.
Number ranges and coordination with Scotland and Northern Ireland.
Scotland's equivalent is called a CHI number; a similar system is also used in Northern Ireland with each of the three systems using the same format but with non-overlapping number blocks, thus preventing the issue of the same number by more than one system.
Currently issued numbers for England, Wales and the Isle of Man are from 400 000 000 to 499 999 999 and 600 000 000 upwards. Current numbers in England also include 3xx xxx xxxx. Unavailable number ranges include 320 000 001 to 399 999 999 (allocated to the Northern Irish system) and 010 101 0000 to 311 299 9999 (used for CHI numbers in Scotland).