<p>I'm taking the subject test for chemistry this saturday (registered), and I'm just wondering if I can take another subject test and just pay later for it even though I didn't register for it beforehand?</p>
<p>If they have extra test booklets and pay at the site they will allow you to take the test.</p>
<p>Yes, collegeboard will bill you later</p>
<p>As to the post above me: OP already registered for a subject test so another booklet isn’t needed. And you don’t pay at the testing center.</p>