By Kathy Canavan

Even millionaire couples have spats about money, but not as often as the rest of us.

Money is a lightning rod for disagreement in the average marriage. Financial matters are the No. 1 cause of bickering between American couples, according to the American Institute of Certified Public Accountants. 

Money matters lead to about three disagreements a month in the average home, and even more among 45- to 54-year-olds, according to the AICPA. That's more disagreements than occur over chores or even children. It's usually over "needs" vs. "wants," the AICPA said.

And, three out of 10 adults living with a partner have engaged in at least one deceitful behavior related to finances. Ever hide a purchase? The AICPA terms that financial infidelity.

Even in million-dollar marriages, the heartstrings are connected to the purse strings, but only one in four millionaire couples argues about money, according to a new PNC Wealth Management survey.  Among those who do, there's usually a reason - they're young, they got their money through inheritance or divorce or a legal settlement, one is an unequal contributor to household finances, they didn't disclose their finances before they moved in together, or all of the above.

When Mr. or Ms. Moneybags marries a fiancé with nothing but a million-dollar smile, the financial disparity triggers tension in 19 percent of marriages. Within that group, 35 percent disagree on how to spend their money and 33 percent are reluctant to even discuss finances. In 10 percent of the marriages, one partner actually feels less attractive because of the financial mismatch.

[caption id="attachment_16947" align="alignleft" width="300"] Heather Flanagan[/caption]

"It can get very sticky and uncomfortable when one person is coming into the relationship with a lot of family money and the other person has limited resources, especially if the people don't know each others' families very well," said Heather Flanagan, PNC's wealth management director for Delaware. "Some of the fears that the family might have about the intended spouse may not be warranted - or maybe they are - but it's good to get everyone on the same page. You're going to have to have the conversation at some point. You might as well have it now, and the sooner the better."

Honest financial discussions where both parties lay all their (credit) cards on the table can improve relationship at any income level. "If you're really planning for a whole lifetime together, you should know if your soon-to-be spouse has debt, if they're expecting an inheritance, if they own a home. You should know all these things because they can have a dramatic effect on your future," Flanagan said. "It's a delicate conversation, but it's part of the information that would be good to know."

That includes exchanging your credit ratings. "You don't want to be surprised that someone maybe had declared bankruptcy a year before and you didn't know about it," she said.

The most successful marriages rest on financial transparency and trust. Nearly six in 10 millionaire couples fully disclosed their financial situations before they got married, the PNC survey showed. Only 30 percent didn't discuss finances at all. Ninety-three percent said premarital conversations about their finances were helpful. Nearly 8 in 10 said they never even thought about or considered a prenup.

Million-dollar couples who fully disclosed were move likely to pool their money in marriage.  Two-thirds said they pool their Benjamins, according to the PNC survey. Roughly 26 percent keep some things separate, and 7 percent keep everything separate.

Flanagan said there are situations where wealthy couples communicate about money but intentionally opt to keep their finances separate, especially in blended families where spouses are concerned about their own children, in marriages between older people accustomed to managing their own finances, and, sometimes, when one spouse has an inheritance or a family business to consider.

She said millennials generally are very comfortable discussing money, and they have more of an expectation that the female will be an equal financial partner than older generations.

Flanagan said people's assumptions about their spouses are often erroneous. "A lot of people who come in have assumptions about their spouses regarding finances, so, what we try to do is have both people in that couple come in at the same time and have conversations with us and get their assumptions out. What we find is often people make assumptions about their spouses that are incorrect - "˜Oh, my wife doesn't want to know about the finances.' "

If a couple is wealthy enough to call a decorator to blend the furniture they bring to the marriage, they might consider phoning another expert early on:

" I don't know of people who say, "˜OMG, I just got engaged. I should call my financial adviser,'" Flanagan said. "But, when you make other major financial decisions, you consult with an attorney, a C.P.A., a financial adviser. You're planning for your lifetime. It's important to have financial advice."

The high cost of conflicts

A 2011 Utah State University study showed married couples who disagree about money once a week are twice as likely to divorce as those who disagreed less than once a month.

These tips from the American Institute of Certified Public Accountants may help couples stay ahead of their finances together.

• Regularly review credit card accounts and bank statements and credit reports together.
• Set a weekly money date to review bank statements, credit card statements and credit reports.
• Split the financial duties to assure a check-and-balance system. Switch duties on and off or make one spouse the bill payer the other the money tracker who follows investments.
• If you need one, hire a financial adviser to diffuse or avoid tension.