Billy - Atlanta, GA
Good question that a lot of people are unclear on. You can take the ACT in the beginning of your senior year. Any college in the US will accept it. So the September, October, and even the December tests give you more chances to improve your score. Although, if you are applying for an early admission program, December and possibly October may be too late.
If you feel like your score is too low for a certain college, wait to send in your application. You don't want to get rejected before they can see your great new ACT score. Just make sure you don't miss the deadlines!

