Changing Subjects on Test Day

I originally signed up for Math I, but now I want to switch to Math II. When I tried to change my registration online, it said that I could do it the day of the exam. I read somewhere that Collegeboard can deny you the switch if they run out of resources (I’m guessing testing booklets?)

Is this true? Am I guaranteed the switch or will I have to risk it on test day?

Thanks in advance.

You can switch to and from any subject test on the day of the exam, guaranteed. The only ones that are not possible to switch into are the foreign language tests with listening. Every subject test is in the same booklet. You do have to tell the proctor BEFORE the test begins once you are at the test center. They can’t run out of test booklets because you already signed up to take Math 1 and it’s in the same booklet as Math 2. You will be fine. Good luck!