<p>im only signed up for 2 tests (bio and math2c) but i want to take three(ushistory), can i add a test on the test day or should i call them and change it now.</p>
<p>When you go to the test center, simply take all three tests. You will get a bill for the extra test in the mail (no late fee or anything, just the price of the extra test - it's under $10.)</p>