Here's an alarming thought:

Many managers hang on to employees they should have fired a long time ago.

The reason?

Deciding to fire someone is an extremely uncomfortable one to make, and managers are as afraid of making a firing mistake as they are of making a hiring one.

So managers put it off until they're 1 million percent certain, and in the meantime, things get worse.

The answer to that question depends on how you keep track of an employee's success or failure on the job.

It's not a simple matter of looking at a person's deliverables and comparing them with actual results. While you should track performance metrics, they can't be the sole basis for deciding whether to keep someone or to let them go.

After all, numbers can be fudged and manipulated. And sometimes, people can have good reasons for not meeting their targets, reasons that don't warrant getting fired.

So I like to keep track of three key areas: culture fit, job performance, and an acid test.

We do this by asking the following critical questions. The first two sets of questions are from Gino Wickman's book, Get A Grip: How to Get Everything You Want From Your Entrepreneurial Business.

Do They Really Belong Here?

The first thing we keep track of is culture fit or the employee's alignment with organizational values, because healthy workplace culture is essential to success.

To check for culture fit, we ask: Does the employee exhibit each of our core values most of the time, some of the time, or a little of the time?

If the answer is "some of the time," then the manager reinforces the value's importance and how it contributes to a collaborative, friendly, and productive work environment.

We want the employee to recognize why demonstrating the value is important in their role, and to have a desire to work on it. Then they and their manager can formulate a strategy for how they can better internalize and demonstrate the value.

But when an employee exhibits one or more core values "a little of the time," the situation is serious.

The manager needs to get to the bottom of the situation, especially when the team member didn't have problems previously. It's possible the person is a good fit for the organization but is in the wrong role.

Other times, it's clear that the person needs to move on.

Do They Get The Job Done?

The next questions relate to the person's role that they were hired to do. When it comes to their job, do they get it? Do they want it? Can they do it?

If the answer to any question is "no," then the manager and employee work together to identify and address the issues. The solution could be as simple as coaching or training the team member. (Learn some unusual ways to improve performance.)

Other times the best option is to move the staff member to a different role, especially when there's a good culture fit. I've seen a few people deliver lackluster performance in the role they were hired for, but do brilliantly in a different role.

Do They Pass The Acid Test?

My management team goes over every member of the organization and asks, "If this person weren't already working for us, knowing what we know now, would we hire him or her today?"

This acid test is based on the accounting principle of zero-based budgeting. This principle forces you to ask if each expense item, including the ones you've been paying for for months or even years, is still aligned with your goals and objectives.

It's a good approach to take with your team members, too.

Sometimes the answer isn't a simple "yes," but it's, "Yes, knowing what we know now about this person, we would hire them again today... but in a different position."

Then it becomes a matter of finding the right role for them in your organization.

But sometimes the answer is an unequivocal "no."

Then it's clear things are not working out and you have to let the person go.

Firing someone is never easy, and it's not a decision to take lightly.

But if you're clear on what's important to you, your business, and the rest of your team, often the decision is clear, and the employee in question isn't even taken by surprise.

Published on: May 17, 2016
The opinions expressed here by Inc.com columnists are their own, not those of Inc.com.