zip + 4: 02123-4507 The check digit is: 6 98765-4321 The check digit is: 5 68506-2708 The check digit is: 8 48381-2307 The check digit is: 4 zip + 4 + 2: 01234-5678-90 The check digit is: 5 28903-1234-78 The check digit is: 3 68002-1327-19 The check digit is: 1 error correction problems: 6702x-5804 x=9; the check digit is: 9 30412-710x x=5; The check digit is: 7 58104-2x02 x=3; the check digit is: 5