Millions of Americans are cheating on their partners financially, a new study shows.

According to CreditCards.com, 29 million American adults have a secret savings, checking or credit card account they are hiding from their parter. The study shows the sneakiest account holders are millennials.

About 2 percent of people say they would end a relationship if they learned the other person had more than $5,000 in credit card debt. But more than 80 percent say while the debt matters, it would not be a deal-breaker.

"The solution is full disclosure. When you have a couple they really need to get together and have good communication," says financial expert Dan Geltrude.

Experts cited in the study say regular meetings over financial matters can help keep a relationship strong.