Why we should all go Dutch on Valentine’s Day

Across Europe, nearly a third of couples are keeping financial secrets from their partners – apart from the Dutch, a new survey has found.

Just 13 percent of the Dutch consider keeping money secrets from their partners to be normal behavior, with only 2 percent hiding debt, 13 percent hiding savings and 11 percent hiding their exact earnings, according to the ING International Survey on Savings, which studied the habits of more than 12,000 consumers in an online poll across 13 European countries.

That compares with the supposedly more romantic French, where around 42 percent are keeping money matters in the closet, the study found.

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"One of the things we know about the Netherlands is they tend to do financial education quite early. They tend to be responsible with their money," Ian Bright, senior economist at ING, told CNBC.

It's not only about spending, saving and debt. More than 10 percent of European couples are in the dark about how much their partner is earning, with the number rising to around one in five in the U.K., Romania, Turkey and the Czech Republic, the study found.

Leon Neal | AFP | Getty Images

Choosing to conceal financial information could be an indicator of whether a relationship will last -- or whether someone should be considered as a partner. A survey of nearly 200 Certified Divorce Financial Analysts cited money as the third leading cause of divorce, behind "basic incompatibility" and "infidelity."

Read More Bypass 'divorce month' by getting honest about money

"Amongst those who were divorced, there were 40 percent across the whole of our sample survey who said 'I think it's normal to keep money secrets from each other.'" Bright said. "When you ask people who are actually married or in relationships, it's down at around the 30 percent level."

As people got older, they become even less likely to keep money secrets, he said.

To be sure, some of these surprises may be pleasant ones.

"European consumers are more likely to conceal a savings account than a debt," the study said, finding that 17 percent of Europeans are hiding savings, compared with 14 percent hiding debt. But even then, 19 percent are concealing some of their spending.

—By CNBC.Com's Leslie Shaffer; Follow her on Twitter @LeslieShaffer1