Should I wait to submit my applications?

I currently have a solid score on the ACT that I am happy with, but I think I can do a little better. I am taking the September ACT and was going to apply to some schools before then. Do you think that it is in my best interest to just wait until I receive my September score to submit my applications? Or should I just indicate on my application that I am taking the September ACT?

It depends. Do you need a higher ACT for those schools? What is the score? What are the schools?