It’s been said that the only place people reach their full potential is on their resumes. In fact, business professionals have been stretching the truth since the first resume came off a typewriter. But that doesn’t make it right.

Today, background screens and reference checks typically reveal discrepancies in about half of job applications (46%), according to ADP, a large HR, payroll, and benefits administration firm. This includes lying about work history, falsifying or exaggerating education, or claiming to have non-existing licenses.

We’ll take this statistic even further. If nearly half of people lie on their resumes or job applications, how many stretch the truth in sales letters, marketing brochures, and sales presentations? A lot! However, not every instance results from bad faith. Instead, many business professionals claim expertise unwittingly. They’re excited about getting the gig and truly believe they can do the work. But unfortunately their self-perceptions and objective capabilities are out of synch.

Here are some common ways people deceive themselves:

• Sometimes they assume they can quickly amass the expertise after getting hired. But then they find that the learning curve is more difficult and time consuming than they thought.

• Other times, they overestimate their own capabilities or underestimate the difficulty of the assignment or the uniqueness of the customer’s request.

• In still other cases, fudging takes place because a company has a culture of “close the sale at any cost.” So people come under intense pressure to make unfounded expertise claims even though they wouldn’t under normal circumstances.

Regardless of the cause, claiming to have expertise you don’t have can create customer dissatisfaction and complaints, ultimately eroding your reputation. And as it weakens, it becomes harder to acquire new customers as negative word of mouth scares off interested buyers.

Now, although this scenario happens in all industries, it’s less likely in highly regulated ones where the law mandates what you can call yourself and how much training you need. Think construction engineers and brain surgeons. If they lie about their expertise and put up a building that collapses or conduct an operation that paralyzes or kills a patient, there will be serious, potentially career-ending, consequences.

However, in non-regulated fields (say, business coaching or management consulting), there’s no legal barrier to claiming expertise you don’t have. Sure, you can’t promote product A, but deliver product B since that would violate advertising laws. But you can easily promote expertise C, but deliver a shoddy version of C, with limited downside risk (excluding damage to your reputation).

So when can you ethically claim expertise and when shouldn’t you? Here are some guidelines to consider. Claim expertise . . .

• When you can execute a project immediately upon closing the sale. If you must begin a course or otherwise climb a learning curve for days or weeks, then don’t claim it.

• When you’ve done the exact or nearly exact type of work a number of times in the past.

• When prior clients can attest to the quality of your work and are willing to provide written testimonials or online reviews.

• When other professionals in your field have begun referring clients to you for that work.

Don’t claim expertise . . .

• When you have never done the work before.

• When learning to do it will take days or weeks.

• When you’re feeling pressure to close the sale at any cost.

• When the customer is a “center of influence” and you’re not totally certain of your capabilities.

• When the project sounds intriguing or tempting, but you have doubts about your skills.

Bottom line? In regulated industries, never claim expertise you don’t have because you may end up getting sued or losing your license. In non-regulated industries, resist the temptation of making sales through exaggeration. You may increase revenue in the short term, but weaken your reputation (and ultimate success) in the long run.

What’s more, think about the marketing advantage of being one of the few “straight shooters” in your field. When people realize you always deliver on your claims, they will tell their family and friends. As a result, your reputation will soar, as will your closing ratios. That’s because in an era of rampant lies and exaggeration, truth tellers win big!

For more information on selling ethically, visit our Ethics Center.