In the state of indiana, i know the age that child support terminates is 21. Do i need to file a petition with the court to terminate this obligation?

You asked this question a while back, but the law changed recently to change the age of emancipation to 19.  There is still a provision for college expenses that can be allowed under the law.  You may need to file a Petition so that you can terminate any Income Withholding Order that is currently active.