If you need to give bad news an article by Sara McCord suggests,

• Find the right time that makes the most sense for the other person and think about whether he or she may consider the issue urgent or not. If you think you need to break the news immediately explain why you think there are special circumstances justifying your interruption.
• Craft your message and tell the end of the story first. What went wrong and what’s the impact? Apologize if you think it’s appropriate, talk about what you think may have contributed to the problem and suggest what to do next or ask for advice on what the next step should be.
• How you deliver bad news will shape the reaction. Your tone should reflect the seriousness of the predicament because the other person should appreciate your sincerity. Don’t overdramatize an issue that you were able to get under control. You might appear to be trying to make yourself look like the cavalry coming to the rescue, while the other person may see you as the person who allowed the situation to get out of hand.
• If the situation is serious and of a personal nature (for health or family reasons you need to step away from the case and have a colleague take over) a less-is-more approach might be the way to go. You can add more info as necessary in the future.
• These conversations can be problem-focused or solution-focused. You can’t control the questions you’ll be asked but you can choose how you structure your answers. After talking about the problem you can propose the next steps or talk about what’s needed to come up with a response. If the question goes back to the problem, explain why you think your action plan will prevent a similar issue from coming up.