Reference 9021 means math error which is IRS speak for they changed something so it calculates different. It does not mean that there is an aactual miscalculation based on what you entered. It is usually due to missing income that was reported to the IRS but was not on your return. It could also be if you reported the correct income but entered it in the wrong place.
**Disclaimer: This post is for discussion purposes only and is NOT tax advice. The author takes no responsibility for the accuracy of any information in this post.**
