Check digit verification. Authorized ID numbers (such as and employee number) can contain a check digit that is computed from the other digits. For example, the system could assign each new employee a nine-digit number,Then calculate a tenth digit from the original nine and append that calculated number to the original nine to form a ten-digit ID number. Data entry devices can be programmed to perform check digit verification by using the first nine digits to calculate the tenth digit each time an ID number is entered. If an error is made in entering any of the ten digits, the calculation made on the first nine digits will not match the tenth, or check, digit.