Nearly three in five of these folks say they hid cash from their partner or spouse; 54% hid a minor purchase; 30% hid a statement or a bill; and 34% said they lied about finances, debt or money earned. Nearly 20% of this group said "financial deception" led them to separate combined finances and 16% said it ultimately resulted in divorce.

Women were more likely than men to say their partner or spouse lied to them about finances, debt or money earned (65% vs. 47%).

"Couples should talk openly about money, and do so early in the relationship," says Ted Beck, president and CEO of the endowment. "Each person should understand their partner's values about money. In doing so, they have a better chance to build a more stable relationship, both emotionally and financially."

But where such honest dialogue is lacking, a variety of red flags may signal trouble ahead for your relationship. Some of those you may see waving:

1. Keeping a 'secret' post office box or hiding mail
Your significant other may be trying to hide serious debts and foolish credit card charges alike from your prying eyes. If the sight of the mailman sets off a fear reflex, they may be dreading the moment you see one of those "PAST DUE" envelopes, correspondence with a collection agency or threat of legal action.

2. Dodging questions about their financial history/credit rating
Marriage brings with it the union of all things financial, including credit ratings. For many couples, that poses no problem and it's accepted that the good and bad will average out to a happy (and hopefully still creditworthy) equilibrium. If the mere effort to discuss your partner's financial background hits a nerve, though, their reluctance probably confirms your suspicions.

3. Letting you pay for everything
We all seem to have a friend who manages to disappear to the restaurant restroom every time the check comes, or who goes full-on ninja invisible when it is his/her turn to buy a round. If your partner is that person, don't assume they are merely a cheapskate. It could be an indication that they can't afford even a simple night out, and that could suggest damaging debt.

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