Depends on the school. My school only lets you take it once, if you fail you must wait 1 year to re-take it. If you fail a 2nd time, you are ineligible to apply to their program. A bachelor program I am looking at allows you to take it twice with a two week waiting period after the first time. If you fail it twice, you are ineligible to apply to their program as well. It's all dependent on the school, so you need to contact the schools you plan on applying to and ask them what their rules are on re-taking the exam.