If you're unsure if you already have a USI, the government provides the following Find my USI options:

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 security questions: You will need to know the answers to your security questions.
4. Personal details and an identification document: You will need to have a valid form of ID that matches your USI details.

Please refer to the USI government website for more information.