gailewells I assume you are setting up your assessment as an anonymous link that can be posted inside of a course (these work well for asynchornous courses with rolling starts and self-pacing). In that case you would want the test taker to fill in their email address to receive credit for the exam. This can be added as a question in the survey/assessment.
However, if this is a synchronous course with a specific date for testing and class roster, you may consider using a contact list that you can either:
1) assign personal links
2) distribute through the mailer
3) or use an authenticator to tie back to the contact list/SSO
From my time in higher ed, I would recommend almost anything but #3. We found that students signed up for a class and were using email with the instructor. But when they had to fill in that email address to access the assessment they were failing time and time again. We never quite figured out what was going on (typos, entering the wrong addresses...). But there were several times I had to increase the number of allowable attempts in the authenticator to more than 5 so students could log in successfully ---- please note these were adult learners in a noncredit class so the class wasn't their first focus.

@bstrahin that was a correct assumption - yes anonymous link that can be posted inside of a course is what I was looking for. I appreciate that info and I've added a final question where the assessment taker's name, company, and email address can be recorded. thank you!