I didn't know anything about the ACT when I first took it, so I scored much lower than I was hoping (22). I've been studying a lot in the interim, and I'm predicting a composite score of around 30 based on practice tests. My question is whether the ACT will think I cheated if my score changes this much. Could I be accused of cheating? What do I do if this happens?
Tests that show an improvement of 6 composite points or more over the course of a 20 month period are flagged for review by the ACT. The ACT will compare your test to the tests of people sitting near you who had the same test format to check for suspicious patterns.
If your test is flagged, it doesn't mean that your score will automatically be cancelled, but it does mean that you should probably have some justification on hand for your significant improvement. You can show the ACT evidence like high grades in school or other high standardized test scores to validate your score change.
Examples of evidence include:
PSAT Scores
AP or IB Scores
SAT Scores
Signed statement from a prep program or tutor saying that you showed significant improvement on practice tests
Ask ACT to look at your test booklet scratch work and compare it to your answers (this would show that you were doing your own work)
You can also choose to retest for free or have your score cancelled and get a refund, but if you didn't actually cheat you should first try and prove your innocence with one of the above pieces of evidence.
Source: https://blog.prepscholar.com/sat-act-cheating-accused-what-to-do