quote from ACT website:
How do I delete a test date record?
If you would like us to delete your scores for a particular test date from our records, you must request it in writing. Provide us with your name and home address, and we will mail you a form to complete and return to us. We will then permanently remove your record for that test date from our files. All scores from that test date will be deleted.
ACT Institutional Services
P.O. Box 168
Iowa City, IA 52243-0168