NHS Number Validator
Validate UK National Health Service numbers. Excellent for your tests.
How NHS validation works
The validator checks if the input is exactly 10 digits. It calculates the weighted sum of the first 9 digits using weights from 10 to 2.
If the division remainder indicates a check digit of 10, the number is rejected as invalid. A remainder of 11 maps to check digit 0, and other values must match the 10th digit.