Is your spouse committing financial infidelity?

Couples at the altar generally don't promise to love, cherish and be completely honest about all financial information from this day forward. Maybe they should.

A new report from CreditCards.com shows that some 6 million Americans have secret bank or credit card accounts that they conceal from their spouse or partner. Two out of three times, the ones hiding the accounts are men.

A more common deception is spending $500 or more on a purchase without telling a spouse or partner. About one in five Americans say they have done this, and again, those people are more likely to be men.

CreditCards.com describes such behavior as "financial infidelity" and says it can be damaging. "These secrets are a recipe for disaster," said Matt Schulz, CreditCards.com's senior industry analyst. "If you and your significant other aren't honest with each other about what you're spending, you never really know how much money you have, and that can lead to big problems."

Hidden credit card use can disrupt marriages. One in 10 people say those purchases played a part in their separation or divorce, according to a 2013 survey by British financial site Moneysupermarket.com. About a third of the spouses in the survey said they hid the transactions out of concern their partner would get angry. Another third said they knew their partner would disapprove.

But some spouses appear to be just fine with secret purchases. Nearly one in three men say their spouses or partners can go right ahead with the big buys, although only 18 percent of women feel the same way, CreditCards.com reports.

So what's the limit? How much can Americans spend without feeling like they have to tell their partners? For some couples, $100 seems to be the maximum amount. About 31 percent of those surveyed said their partners shouldn't spend more than that without disclosing it. That included 37 percent of women but only 23 percent of men, according to CreditCards.com.