Can I take more subject tests than I signed up for?

Test Preparation SAT Subject Test Preparation
1

I looked it up, and it seems you can, but the article was from 8+ years ago. If I’ve only signed up for one, can I decide to take three on test day? If so, how much extra would it cost to take each one?

Thanks

2

Yes, so long as one of the tests is not a foreign language with listening.

$21 per test AFAIK, for which you’ll be billed.

3

Excellent, thank you!