When we think of cheating, we typically envision a Carrie sneaking around to see Big type of situation. We don't always picture checking and saving accounts—still a scandal, albeit a slightly less nail biting one. But financial infidelity is a real problem plaguing many couples.

Secretly keeping a separate bank account, hiding what you’re spending, or hiding how much debt you have can all be considered financial infidelity. And almost 39% of coupled up adults in the U.S. report that they’ve been financially unfaithful at one point or another, according to a new Bankrate.com survey of 2,500-plus adults who are married, in a civil partnership, or living with a partner.

Younger generations are more likely to report being financially unfaithful: 64% of Gen Zers and 54% of millennials say they’ve kept secrets about money from their partners, compared to just 29% of both Gen Xers and baby boomers. Gen Z and millennials are mostly staying mum about their spending habits and debt levels.

Even though it’s the younger generations who are more likely to be dishonest about their finances with their partners, they’re also more likely to say financial infidelity is worse than physical cheating—22% of Gen Zers and 21% of millennials, compared to 5% of boomers and 4% of Gen Xers.

More than half (52%) of all adults surveyed said that financial unfaithfulness is just as bad as physical infidelity, while 48% think the latter is worse.

It might be surprising that Gen Z and millennials are so hush about their money habits with their partners considering that they’re destigmatizing the taboo of talking about money. Gen Z is especially vocal about salary transparency as a way to lead to greater pay equity. But this behavior doesn’t always translate to real life openness in talking about finances with significant others or friends.

Perhaps they know that money is the number one thing couples argue about. Financial infidelity in particular can rock a partnership, Andrea Woroch, a personal finance writer, told Business Insider. "Financial infidelity may occur after years of built-up financial tension in a marriage or as a result of poor communication and different dreams," she said. "In other times, it could come from a deep-rooted emotional issue that needs to be addressed.”

But what exactly constitutes a financial lie may be more blurred for younger partners, who are more likely to keep their finances separate from each other, Bankrate found.

“Many couples want some form of financial independence, which is totally fine as long as it’s acknowledged ahead of time,” Ted Rossman, senior industry analyst at Bankrate, said in a press release. “Having a separate bank account or credit card works for a lot of people. The key is to agree upon the general parameters. Secrets can take on a life of their own and undermine the relationship.”

This story was originally featured on Fortune.com

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