Whether it’s something as simple as printing the company brochures on the wrong type of paper or serious as emailing confidential pricing information to the wrong client, it’s not a matter of if a new employee will make a mistake, but when. The good news is that supervisors know you’re bound to make a mistake—as they undoubtedly have—and what is most important to them is how you handle it and if you learn from it. Some tips:
Act quickly: Unless you can solve the problem yourself and it’s no biggie, you should immediately tell your supervisor about the mistake. Never wait to see if it is noticed before you speak up. Waiting could make the mistake lead to a bigger problem than you thought, which will really irritate supervisor. Worse, if he or she thinks you knew about the mistake but didn’t say anything, there will be a serious loss of trust.
Own it: Resist the urge to blame someone. It’s fine to say that you didn’t know that something was not permissible and thus made a mistake, but don’t throw someone else under the bus by saying you were never told by [fill in the blank] that something was not permissible and that’s why you made the mistake. As you are still learning, you supervisor will likely know that a mistake you made came as a result of being ill informed—let them find and address the issue with the guilty party if they choose to. When explaining your mistake, be honest as to how and why it occurred and try to keep the explanation simple.
Don’t make a big deal out of it: Don’t amplify your mistake and make it stay on your boss’ or colleagues’ mind by continuing to apologize about it. What is done is done. Once you’ve said you apologize, gave an explanation, and worked on resolving the issue, move on and stay quiet about it.