1. Choose your timing
While it's important to let your boss know about urgent mistakes at work as soon as possible, you want to ensure you will have her full attention and enough time to explain the details. Request a quick, private, in-person meeting with your manager. If you work at different locations, suggest a Skype call or Web conference. A face-to-face meeting, even virtually, is a more effective way to communicate serious mistakes at work than by email or a phone call.
2. Know your audience
How to approach your boss with news about mistakes at work may depend on his communication and leadership style. If he's the analytical type, you may be able to cut straight to the chase, spell out the problem, offer up a range of solutions and get back to work. But if he's more collaborative, you may need to give more background on what happened and why, and then work with him to find a solution.
3. Answer honestly
When talking to your manager about mistakes at work, be prepared for questions — lots of them. She'll likely want to know how it happened, your role in the event and who else might be involved. Be direct and respond with facts. Avoid making excuses, justifications or stories. Take responsibility for miscalculations and oversights.
4. Be a problem solver
Bad news is always easier to accept when a path to resolution is clear. Make a timeline of events so you and your manager can troubleshoot what went wrong, where and when. Then, outline possible next steps.