16.1 Check Digits U.S. Postal Service Money Order - Video

Key Ideas

  • Many frequently used types of error-detecting codes for identification numbers include an extra digit (usually the last digit) called a check digit. The check digit can be compared to the rest of the number to check for validity.
  • For a U.S. Postal Service money order, the check digit (the last digit) is the remainder you get when you divide the sum of the other digits by 9.