Is it illegal to include statements in an employee review which have been proven false?

My most recent job performance review includes the statement that I do not work a full 40 hours per week. I proved that the supporting data used for the accusation was inaccurate on many days (I had several emails which were sent AFTER the report said I logged off my computer on several days). Furthermore, the IS employee who provided my boss the report stated that they currently have no accurate method of measuring employee's login and logoff times, and the report should not be used to prove the number of working hours.

I asked my supervisor to remove the statement of not working 40 hours per week since I proved it as inaccurate. He refused to remove the comment, but instead allowed me to write a rebuttal letter that would be attached to my review.

I am employed in Michigan, and am considered as an "at will" employee. I do not work under any contract. Is a supervisor free to include any information he/she wants to in an employee review?

Yes they are allowed to include any information they want in your performance review, as long as you are allowed to submit a rebuttal and both items are kept on file.

What your supervisor did is what I would have suggested. An appraisal/review is for the most part opinions. You have the right to disagree.

Technically, you have not proven that you have worked at least 40 hours. You have shown that their records do not prove that you have not. There's a difference.

Unfortunately, there is no law that states she has to give you an accurate review.

If you were not fired or written up for it, write the rebuttal and let it go.

If you keep pressing it, I knew a guy that lost a $98K a year position because he threw a fit that his review wasn't written "correctly". They got sick of his complaining and just fired him.