If you're unsure if you already have a USI you can check Find my USI in one of four ways:

1. Email address: Your USI will be sent to the email address in your USI account
2. Mobile number: Your USI will be sent to the mobile number in your USI account
3. Personal details and check questions: You will need to know the answers to your check questions
4. Personal details and an identification document: You will need to have a valid form of ID