Overwhelmed at Work? How to Master the Art of Saying No.

This piece originally appeared in AllBusiness.com.

What are your options when someone encroaches on your selling time? Most likely your sales will suffer if your time is spent on tasks other than selling.

However, unless you’re the CEO, there will be times when someone asks you to do something that you are unable to do. You may have already experienced times in sales when you’ve wanted to say no to a superior, but what held you back was fear of the consequences.

Here’s how to sell the “no.”

Know your boundaries.

Chinese military general and philosopher Sun Tzu said, “The supreme art of war is to subdue the enemy without fighting.” In business, the best “no” is the one you don’t have to say.

However, any time you turn someone down, you have to deal with certain issues: you might hurt someone’s feelings; a superior might think you are not a team player; a peer might think less of you. But what if the person asks you to do work that clearly isn’t your responsibility? It would be extra work for you and you don’t have the time–you want to say no.

For more on leadership advice, watch this Fortune video:

As Sun Tzu suggests, the best no is the one you don’t have to say. When the work that’s requested is clearly beyond the scope of what you do, ask, “Why are you asking me to do this job?” Pay attention to the tone of your voice. You don’t want to sound like you are accusing the other person; you simply should be asking for information.

There may actually be a very good reason why the person is asking you. Maybe a superior wants you to gain valuable experience that would prepare you for a job promotion.

Or the person may not have a good reason. You may find out the reason you were asked is because you’re a nice guy who often takes on additional responsibilities and does them well. Nice guys often get taken advantage of in business. You can then reply, “It sounds like I’m not the best person for this task,” if you determine that you shouldn’t have been asked in the first place. You don’t have to say no directly to make your point.

Talk about fairness.

Another way to say no is to reprioritize the work you have.

Let’s say you’re asked to do additional work that takes you away from your selling, and you’re stressing over having to meet your sales goals and completing the added work in a satisfactory way. I was asked to provide business planning support to management one day a week in addition to working my sales territory. My sales goals weren’t reduced 20 percent to account for my time away from my business. I managed to do both jobs, but the stress was too much. Even though I was enjoying the new work, overall it was too much because I felt like I was being taken advantage of.

So I scheduled a meeting with my manager where I explained the situation. I said that I was doing my sales job, but with 20 percent less time, and my quota hadn’t been adjusted 20 percent less. I asked him, “What do you think is a fair way to address my situation?” By focusing on what was fair and asking instead of telling, we had a dialogue.

When you tell management “no,” it’s better to have a dialogue and not make threats or get emotional. And I certainly could not say, especially being female, that I felt taken advantage of.

Since my manager needed my sales numbers more than he needed my business planning input, he stopped pulling me out of my territory to do his work. He probably didn’t realize that he was placing an unfair burden on me.

Ask about time.

I could have framed my discussion with my manager from the point of view of time; there is only so much time in a workday. I could have said to my boss, “I’m managing a sales territory and working on business planning. Which tasks do you want to take away from me so that I can manage my territory and do the business planning?” It would have been his choice to hire another salesperson or decrease the time to work on business planning.

Just know that you can always say, “I need to check my calendar and get back with you”–even though it only postpones the answer. At some point you must learn a firm and polite way to say no and be protective of your time.

Eleanor Roosevelt once said, “No one can take advantage of you without your permission.” Remember that the next time someone asks you to do work and you want to say no.

Maura Schreier-Fleming is president of Best@Selling, a sales training and sales consulting company.