You can get your USSF ID Number by doing the following:
1) Click on ‘My Info’ on your Game Officials homepage.
2) Click on ‘Contact Info’. Your ID number will be shown near the bottom of this area.
If you just took an New Referee course to get certified as a referee, it may take several months for the national office to assign you a USSF ID and appear. You are still eligible to referee without an assigned ID number; it should not be a requirement to receive assignments as assignors should still be able to verify your certification.