Can I take the SAT and the ACT tests?

I'm going to be a sopre in high school next year, so I'm taking the PLAN and the PSAT, as well as when I'm a junior. But I haven't been able to get a clear answer from anyone--can I take both the SAT and the ACT when my senior year rolls around? Yes, I understand all of the differences between them and the advantages of each, but i just need to know if I'm allowed to take both. Thanks!