[header] How to kindly tell your boss that he or she is mistaken [title] Decide how important the issue is. [step] Telling your boss they're wrong can have an impact on your relationship. Therefore, you want to make sure the issue is worth discussing before bringing it up. 
If your boss is wrong over something minor, alerting them to this may come off as condescending. [substeps] How much is the issue really affecting your work life? If you disagree with your boss on something minor, such as policies regarding lunch breaks, it's probably only a minor inconvenience for you and other employers.