I signed up for the the Math 2 and Biology SAT II exams, but now that the test date is growing near (December), I’m realizing that I am nowhere near ready for the Math 2 exam. Can I only take the Biology exam on the test date instead? Will me not taking the Math 2 exam show up as a failure to take the exam in my records? Or will it just be cancelled, and it’ll just look like I never signed up for Math 2 in the first place?
"If you decide to take fewer tests than you signed up for, just turn in your answer sheet before the next test begins. Remember, though, that once you start answering a test, you can’t decide not to take it — you’ll have to cancel all tests taken that day to avoid having it scored.
You can also add a test on test day, if it’s being given on that day. Just remember that the exceptions listed above will apply. You’ll be billed for the tests you add."
https://collegereadiness.collegeboard.org/sat-subject-tests/taking-the-test/test-day
In other word, if you don’t take, there will be no record of an attempt.