By Andrea Woroch

How do you spot financial infidelity? US News and World Report asked relationship expert Susan Winter for the telltale signs to look for in your mate’s behavior.

Honesty is essential to a healthy and long-lasting relationship, and any breach of trust could rip two people apart. While most people think of betrayal as being emotional or physical in nature, financial infidelity can be equally crippling and is more common than many realize.

In fact, according to a survey by the National Endowment for Financial Education, two in five Americans admit to committing financial infidelity against their partner, and 75 percent of respondents who experienced this type of deception said it affected their relationship. Such infidelity may include hiding a purchase, bank account, statement, bill or cash from a partner or spouse to more drastic deceit such as lying about the amount of debt owed or the amount of income earned.

Lying about money matters can vary in severity, from hiding a purchase to concealing gambling debt. Regardless of the degree of betrayal, however, one thing is certain: It can damage the trust two people have built and ultimately jeopardize household budgets and future goals. In extreme examples, couples can lose homes, cars and other possessions if behaviors go unchecked for too long, experts say.

“Financial infidelity could be as benign as not telling your significant other that you made a small purchase, like a pair of shoes or sunglasses, to hiding thousands of dollars of credit card and other debts from that person,” says Shannon McLay, founder and CEO of The Financial Gym. “Just like physical infidelity, financial infidelity creates a rift between two people that can start out small, but grow into something more significant.”

While this deceit may be hard to uncover, learning the warning signs can make it easier to spot and ultimately help couples address the financial issues before they escalate. Here are several things to look out for.

Refusal to discuss financial matters. A partner who is withdrawn or defensive when discussing the household budget is likely withholding something. People who are lying about money often avoid disclosing financial information.

“If the person you are with is not open to sharing their financial situation or discussing the specifics like bank account or credit card balances, they are probably hiding something,” McLay says. “I encourage clients to get financially naked as soon as possible and share all of their financial information.”

McLay recommends that married couples manage all bills from joint accounts or combine accounts into one system such as to track household spending activity. If one partner refuses, the other may question him or her about financial habits.

A flurry of packages or new items around the home. Concealing purchases is one of the most common forms of fiscal treachery, and though it seems innocent, the person in question may have a shopping addiction or may have racked up excess credit card debt that needs to be addressed. If new items have popped up around the home and these purchases were not discussed beforehand, it’s important to take this situation seriously.

“If you see extra Amazon boxes in the recycling bin or more items in the closet, and you didn’t take part in the decision to buy them, then your loved one is probably hiding something from you,” McLay says.

Emotional swings and erratic behavior. When a significant other begins acting out of the norm, it can be a clue that something is going on behind closed doors. Experts suggest looking for “tells” or behavioral patterns that change in a way that’s clearly noticeable, from spending more time away from home or at the office to acting more distant than usual or perhaps overly generous and attentive.

“Lying isn’t comfortable for all individuals. Therefore, your mate will probably have ‘tells’,” says Susan Winter, relationship expert and author of “Older Women, Younger Men: New Options for Love and Romance.” “These are the unconscious physical reactions to either your questions or to normal conversations that brush up against the topic of assets.”

Being secretive with tech. Smartphones and computers contain sensitive personal and financial information, and a partner or spouse who suddenly becomes secretive when it comes to their gadgets should be considered suspicious. Such enigmatic behavior may include locking the device with a new password, leaving the room to take a call or text or covering up the screen when other people are around.

“In general, your partner may be hiding something if he or she quickly closes all the screens on a computer or phone when you enter a room,” says Andrea Syrtash, relationship expert and author of “Cheat On Your Husband (With Your Husband): How to Date Your Spouse.” “If your instinct tells you something is off, listen to that.”

Strange account activity becomes evident. Unusual activity, such as an odd charge on the credit card statement, a withdrawal of cash at a peculiar time of day or night and a notable fluctuation in account balances are often signs that a partner is lying about their fiscal habits and it shouldn’t be ignored.

“If you come to the point of suspecting financial infidelity, you’ve probably stumbled across some physical evidence that’s allowed you to connect the dots,” Winter says.

How to Approach Suspicions

When concern of financial infidelity arises and evidence of the deception is clear, it’s important to approach the issue carefully and thoughtfully. Confronting a partner will ultimately be stressful and uncomfortable, but doing so in a respectful manner will make it easier for that person to open up.

“If your partner is hiding financial activity from you, it’s likely because they’re ashamed and afraid of judgment,” McLay says. “Make it clear that you want to have the conversation from a judgment-free perspective in the hopes of improving your family’s financial health.”

Once the problem has been addressed, couples have a difficult journey ahead in order to rebuild trust. To do so, however, the reason behind the financial faithlessness must be reconciled first, experts say.

“In order for you to progress as a couple, your partner needs to heal the root cause of their financial infidelity,” Winter says. “Was it an affair? A drug or gambling addiction? Whatever the reason for the financial infidelity, if your partner is committed to healing themselves, then there’s a chance for you as a couple to heal as well.”

Couples who have trouble dealing with such sensitive topics are advised to seek guidance from a third party like a counselor or financial advisor to help navigate the conversation.

How to Prevent Financial Infidelity

Don’t wait until financial infidelity has been committed to take action. Create an environment where each partner can speak openly about their financial needs and wants without the worry of being judged, and meet regularly to discuss financial matters. Planning monthly money dates can be a fun way to review the household budget and approach any potential issues before they get out of control.

“Having regular and collaborative conversations about money allows couples to get on the same page with identifying spending and saving behaviors, setting goals and building trust, all of which are essential to a lasting relationship,” says Paul Golden, spokesperson for the National Endowment for Financial Education.