We all tend to bend the rules a little at work, whether it's tacking an extra 10 minutes onto our lunch hour now and then, or sneaking home a few items from the office supply closet. But if there's one thing you really need to be careful about at work, it's calling in sick when you're not, in fact, ill.

Faking sickness to snag time off is a fairly common practice these days, with an estimated 40% of workers calling in sick when they're perfectly fine. The problem, however, is that employees who do this are increasingly getting caught. CareerBuilder reports that 38% of companies check up on workers who claim to be sick, while 26% have actually had to fire someone for getting caught in the act.

Man sick in bed, coughing

IMAGE SOURCE: GETTY IMAGES.

The next time you're thinking of calling in sick to enjoy a day of leisure, or take care of personal matters, you may want to think twice. Your job could end up depending on it.

Why we lie about being sick

If companies were more generous with their paid-time-off policies, perhaps employees wouldn't have to concoct tales of sneezing, wheezing, and phlegm in an effort to snag a much-needed break. But the fact of the matter is that most time-off policies nationwide leave much to be desired.

The typical U.S. worker gets just 10 paid vacation days per year, and in some cases, that figure includes sick time, as well. But often, an employer will separate vacation and sick time into different buckets, offering a certain number of paid days for each, or in some cases, unlimited time off for the latter. It therefore stands to reason that if you've exhausted all of your vacation days and need, or want, an extra day off, your best bet is to pretend to be sick and avoid taking unpaid time away.

The problem, of course, is that you never know when your employer might call your bluff. You may, for example, be asked to bring in a doctor's note to prove you were ill, and if you don't have one, you could be out of luck. Or your employer might be more stealth about checking up on you than you'd think. In the aforementioned study, 22% of companies drove by employees' homes to verify that they were actually sick when they claimed to be. Talk about being thorough.

Don't fake an illness when you need time off

Pretending to be sick to snag some much-needed time off might seem justifiable, especially if your company's vacation policy isn't particularly generous. But rather than focus on perfecting your faux cough, here's a better approach: Work on being honest with your boss instead.

Your manager might understand that you need an extra personal day to take care of a household repair, help a friend, or just recharge. If that's the case, and you have a good relationship, you can ask if there's wiggle room to give you an extra day off and have you make up the time elsewhere. If you're a good employee with a history of putting in your time as needed and meeting deadlines, you might get the leeway you're looking for without having to deliberately mislead anyone.

Finally, keep in mind that if you are sick at any point during the year, by all means, stay home. Just as it's a common practice to lie about being ill, so is employees' inclination to drag themselves into work when they should really be resting in bed. Your best bet is to just be honest about the state of your health -- no matter what it happens to be. 

The Motley Fool has a disclosure policy.