While alien numbers may consist of 7 to 9 digits, you must enter exactly 9 numeric characters. For alien numbers with fewer than 9 digits, add one zero (0) to the beginning of an 8-digit alien number and two zeroes (00) to the beginning of a 7-digit alien number.
Although the employee is not required to write the Alien/USCIS Number in Section 1, the number is required for E-Verify. If not in Section 1, you may find it on the employee's List A document.