The NHS Number is 10 digits long. The last digit is the "Check Number" or "Check Digit ". This is used to validate the full NHS Number. A calculation is made on the first 9 digits and its sum is compared against the check digit to see if the NHS Number is correct.
- Multiply each of the first nine digits by a defined weight. The weight is shown below:
1 - 10
2 - 9
3 - 8
4 - 7
5 - 6
6 - 5
7 - 4
8 - 3
9 - 2
For example if the 2nd digit is 3 then its 3 x 8. If fourth digit is 7 then its 7 x 4
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Get the sum of the 9 multiplications.
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Divide this sum by 11 and get the remainder
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Subtract 11 from the remainder to get the total
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If the total is 11 then the identifier is 0, otherwise the identifier is the total
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If the identifier is 10 then the NHS Number is wrong
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If the identifier equals the check number then the NHS number is correct