Teens don't lie all the time and they might not do it the same way each time, but your teen is probably going to lie more than once, whether it’s by intention or by omission. Maybe she lies intentionally, telling you exactly what you want to hear so she can get her way. Maybe she lies by omission, such as telling you that the party she’s going to on Friday night will be an adult-supervised party only she forgets to mention that the “adult” is a 21-year-old college student. Lying isn’t a habit you want your teen to continue, which means you need to stop it before it gets worse.
Tell your teen lying is a serious offense, advises Austin-based psychologist Carl Pickhardt, writing at the website for "Psychology Today." When he knows that lying to you is something he will be punished for, it can reduce his desire to do it. For example, tell him that any time he lies to you, you will take away one of his privileges, including his cell phone, using the computer or driving, for an entire weekend.
Encourage her to come clean about past lies, advises Phil McGraw, a child expert and talk show host. If your teen makes lying a habit, she likely will continue to lie in an effort to cover past lies. For example, if she lied to her teacher about visiting her sick grandfather on his deathbed as an excuse for not turning in her homework, she needs to come clean so she doesn’t have to continue lying about her non-existent sick grandfather. She will feel much better when she finally gets her lies out in the open and no longer has to remember to keep her stories straight or risk getting in trouble for continuing to lie.
Discuss the cost of lying with your child. According to Pickhardt, lying makes life more complicated. It makes people lose trust in a person, increases stress from the fear of lies being discovered, and can lead to loneliness by distancing himself from people he lies to in an effort to keep from being found out. Tell your teen that taking responsibility for his lies might not always be fun and he will have to deal with the consequences, but that will end. Lying, on the other hand, lasts forever. He could suffer a punishment now and be in the clear next week or he could live in fear and isolation trying to keep from getting caught.