Free Tool
NHS Number Validator
Verify any NHS number using the official Modulus 11 checksum algorithm. Instantly checks format and validity.
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How NHS number validation works
NHS numbers are 10 digits long. The final digit is a check digit calculated using the Modulus 11 algorithm:
Each of the first 9 digits is multiplied by a weighting factor (10 down to 2). The products are summed, and the remainder when divided by 11 is subtracted from 11 to produce the check digit. If the result is 11, the check digit is 0. If the result is 10, the number is invalid.
A number that passes this check is correctly formatted — it does not confirm the number is assigned to a real patient.