Even when you have a positive relationship, bringing bad news to the boss is something most people would rather avoid. This includes telling the boss, “no,” even when it’s the right thing to do.

Sure, the supervisor should welcome honesty and candor – and most do. However, when delivering a “no” message, it’s also important to know what to tell your boss, when and how.

Katherine Reynolds Lewis of Fortune wrote, “companies that foster a fear-free culture enjoy better decision-making, more ethical behavior and the ability to truly harness the collective brainpower of the workforce.”  Creating and maintaining a positive culture isn’t just the boss’ job. How direct reports share information and team with their bosses for mutual success contributes to a transparent culture as well.

How do you effectively tell your boss “no?”

Communicate when an important result is at stake. If a key project or outcome is at risk, you need to tell your boss. State the situation clearly and provide possible solutions. “The software integration is 2 months behind schedule and 40% over budget. Options include adding a person to the team or finding an alternative vendor.”

Be honest about what you can and cannot do. Speak up if your boss assigns you something that is outside your skillset and more than a stretch goal. However, don’t leave her holding the ball. Suggest what you can do and who might fill the gap. “My skills would be better utilized on the project management end, with Sean on the technical side.”

Prepare the boss and speak in private. Your boss may be less willing to be open to input if it comes out of the blue. Send him an email, letting him know that you have some ideas you’d like to share. Meet one-on-one to explore these ideas without an audience that could have an unanticipated impact.

Say thanks. Even if she doesn’t agree with your perspective, your boss took the time to listen (hopefully). No matter how the meeting goes, genuinely thank her for her time. You’ll build some relationship capital that may be helpful in the future.

When saying no, or delivering any message that might be hard to hear, use as few words as possible. There is no need to use giant words, spin, lecture or defend. Remember the advice of John Kotter. “Good communication does not mean you have to speak in perfectly formed sentences and paragraphs. It isn’t about slickness. Simple and clear go a long way.”