I have submitted my USI information, but it has come back saying that my USI is invalid. What should I do?

The USI number that you have supplied us is incorrect. Please double check the USI you have given us against the USI that you were issued to ensure that there are no errors. If you find no discrepancy between these numbers, you will need to contact the USI Department to find out your correct USI. You can do so by calling 1300 857 536.