Definition: check digit

A numeric digit used to ensure that account numbers are entered accurately into the computer. Check digits are computed when the numbers are generated, and they become part of the number, often at the end. When an account number is entered, the data entry procedure recalculates the check digit and compares it. If not equal, the account number is considered invalid. Following is a simple check digit computation:

  Starting Number:

  2  8  5  0  4  8

   1 - Sum digits = 27
   2 - 2 and 7 = 9
   3 - Append to end

  Account number with check digit at end:

  2  8  5  0  4  8  9