Editor's note: Inc.com columnist Alison Green answers questions about workplace and management issues -- everything from how to deal with a micromanaging boss to how to talk to someone on your team about body odor.

A reader writes:

I'm a relatively new manager (4 months). I am coming from the position of teammate to most of the staff I manage, but they all seem to have adjusted well to my new role and respected my move from peer to manager.

However, I seem to be having an issue with one of my employees regularly sneaking out 10-15 minutes early from work. I've started to catch on, and when I ask, the person says that she didn't take her 15-minute break so that she could leave early (but if that's the case, it needs to be arranged and agreed upon with me), then proceeds to talk my ear off about the weather and everything she did that day and then rushes out the door before I can get a word in edgewise.

I feel that I should be more assertive, but I don't know how to prove my point when this employee has basically found a loophole. I would be okay with this once in a while (and if we discussed it first), but I don't like the sneakiness of it.

Yes, the issue is far less the 10-15 minutes and much more the sneakiness, because it goes to trustworthiness and integrity.

But she hasn't "found a loophole." You say above that your rule is that if she wants to leave early in exchange for not taking her break that day, she needs to get your OK first. She's not doing that, so there's no loophole here. She's just not following your policies and hoping that she'll get away with it.

And the reason she's getting away with it is because you're letting her. It sounds like that's because you're not yet comfortable with the authority of your position. Letting someone do something she shouldn't be doing just because she starts talking rapidly about the weather is not an effective management technique.

Before we get into what you should do about that, I want to first ask whether it really matters if she leaves early. Is she getting all her work done? Is she performing at a high level? If so, you might consider whether it makes sense to give all high-performing employees (not just her) more flexibility with their schedules.

But if that's not the case, or if this is a job where physical presence during specific hours is important, then you need to be direct and straightforward. Set up a meeting with this employee and say the following: "I want to clarify our rules on leaving early. If you want to leave early to make up for not taking a break that day, you need to talk to me about it first so that I can clear it. If you don't have explicit permission to leave early on a particular day, you need to work until the end of the time you're scheduled for."

Then, stick to it. If you see her leaving early again without your permission, you need to call her on it. You can do this in two ways: You can stop her on the spot, tell her it's not time to leave, and send her back to work, or you can talk to her about it first thing the next day. Either way, you need to start setting up consequences at that point.

So you might tell her, "Sue, I was extremely clear about this when we talked last week. Where did we miscommunicate?" Then, assuming that she doesn't explain that she was rushing out the door because of a gunshot wound or some other emergency, you say, "By continuing to do this after we've talked about it, it's turned into something more serious. You're now violating a policy that I've warned you about. I need to be able to trust you to follow our policies. This is a very easy thing to correct and I hope that you will, but if it continues to happen, it could jeopardize your job."

If that seems like an extreme consequence for leaving 15 minutes early, keep in mind that the issue here is integrity, not 15 minutes of time. It's about integrity because she's trying to do something without you noticing it, and she's continuing to do so after you've already warned her. This is a much, much bigger deal than 15 minutes of time; you can't have someone working for you who deliberately tries to get away with things behind your back. (And I can almost guarantee you that with someone who operates this way, there are other problems with how she approaches her work.)

The bigger-picture issue here, though, is learning how to deal with situations where the people working for you aren't performing in the way that you need -- being comfortable raising the issue, correcting the behavior, setting consequences if it continues, then enforcing those consequences, and doing it all in a way that's direct, straightforward, and fair (not defensive or insecure or overly harsh). These are essential pieces of being a manager.

More situations like this are going to come up -- and some of them will be more complicated than what time someone is leaving -- and you'll need to be prepared to handle them. So I'd recommend starting to think about how you're going to handle other types of performance problems, like someone who's bad with customers, or someone who's trying really hard but just not doing a good job, or someone who doesn't follow through on things you ask them to do. Your job now is to handle this stuff, and you don't want to wing it.

Want to submit a question of your own? Send it to alison@askamanager.org.