NHS Number

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A National Health Service (NHS) Number is a unique identifier allocated in a shared numbering scheme to registered users of the public health services in England and the Isle of Man.

The NHS Number is the key to identifying patients — especially when delivering safe care across provider organisations — and is required in all new software deployed within NHS organisations.

References:

• National Health Service (NHS)

• NHS Number

What this crate does

For the full public surface, see docs/api/index.md. For the canonical behavioural specification, see spec.md.

Install

cargo add nhs-number

Or in Cargo.toml:

[dependencies]
nhs-number = "1"

Syntax

The current system uses a ten-digit number in the 3 3 4 format, with the final digit being an error-detecting checksum. An example: 943 476 5919.

Ranges

Currently issued ranges:

• 300 000 000 – 399 999 999 (England)

• 400 000 000 – 499 999 999 (England, Isle of Man)

• 600 000 000 – 799 999 999 (England, Isle of Man)

Unavailable (reserved for other systems):

• 320 000 001 – 399 999 999 (Northern Irish system)

• 010 100 0000 – 311 299 9999 (CHI numbers in Scotland)

Testable (valid by the checksum algorithm, never issued):

• 999 000 0000 – 999 999 9999

For the full table and guidance on choosing test fixtures, see docs/ranges/index.md.

Checksum

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

• The first digit (9) is multiplied by 10.

• The second digit (4) is multiplied by 9.

• And so on until the ninth digit (1) is multiplied by 2.

• The products are summed. Here: (9×10) + (4×9) + (3×8) + (4×7) + (7×6) + (6×5) + (5×4) + (9×3) + (1×2) = 299.

• The remainder when dividing by 11 yields a number in 0–10 — here, 2.

• This is subtracted from 11 to give the checksum in 1–11 — here, 9, which becomes the last digit of the NHS Number.

• A checksum of 11 is represented by 0 in the final NHS Number. A checksum of 10 means the number is not valid.

For two fully worked examples and the in-crate entry points, see docs/checksum/index.md.

Example

use nhs_number::NHSNumber;
use std::str::FromStr;

// A test-safe NHS Number drawn from the reserved testable range.
let input = "999 100 0003";

// Parse a string into an NHSNumber.
let nhs_number = NHSNumber::from_str(input).unwrap();

// Validate the check digit.
let is_valid: bool = nhs_number.validate_check_digit();
assert!(is_valid);

// Round-trip back to the canonical string form.
let displayed: String = nhs_number.to_string();
assert_eq!(displayed, input);

For a tutorial walk-through, see docs/usage/index.md. For runnable programs, see examples/.

Documentation map

License

Multi-licensed under MIT OR Apache-2.0 OR GPL-2.0 OR GPL-3.0 OR BSD-3-Clause. Pick whichever fits your project.