NEW YORK ( MainStreet) — It's called financial infidelity, and it's one of the biggest causes for failing marriages today. All told, about half of all people admitted to lying to their spouse about money.

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"It's not that much different from other kinds of infidelity," says Dr. Donna Tonrey, a licensed MFP and the director of the Counseling and Family Therapy Master's Program at La Salle University in Philadelphia. "Someone is doing something that has an impact on both of them as a couple and is keeping it a secret." If you've committed financial infidelity or your partner has, read this article to know the best way to handle it.

What To Do If You're the Guilty Party

"First, you need to prepare to have a tough discussion with your spouse," says Jacob Gold, a Voya Retirement Coach with ING Financial. "You need to have full disclosure, that's the important first step." This includes getting a detailed account of your financial in-flow and and out-flow. Gold adds that "You need this information so that it's on hand when you have the conversation, which will likely get very heated, very quickly."

Tonrey advises those who have been guilty of financial infidelity to also examine the underlying reasons for their actions. "Sometimes there might also be a power struggle," she says, explaining that "it can give a sense of power to be able to do something with money, but the person doesn't feel strong enough to be honest about it." Exploring the reasons for doing this allows the person to be honest about their motives when discussing the matter.

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Finally, Gold suggests that people have a plan for how they're going to fix the situation. "You have to say, 'This is what happened, but this is my commitment to not having this problem in the future,'" Gold says. He advises that having a third party -- be it a counselor or a financial advisor with whom you already have a relationship -- can help this discussion go easier. "We need to have regular checks in place to make sure that you're working on this and improving it," he says.

What Do If Your Partner Comes to You

But what do you do if your partner comes to you and tells you that they've been secretly spending money? "It feels like a betrayal," says Tonrey, "Once that trust is gone it can be very difficult to get back."

Still, Tonrey is quick to add that "people often rise to the occasion when a crisis occurs." She advises that you begin by listening to the facts, as well as the person's reasons for why this occurred. When they're done sharing, it's time for you to share the impact that this has had on you.