I thought about cheating on my husband while out mountain biking recently. As my friend sailed effortlessly down the rutted trail, my teeth chattered and my hands went numb. That’s when I hatched my plan to splurge on a cushy new bike—and hide it in our neighbor’s garage.

Why such sneakiness? You see, every woman has her downfall, be it new shoes, spa days, or in my case, skis, kayaks, and bikes. My husband is, understandably, a bit frustrated; my equipment threatens to keep his car out of our garage. The last time he agreed to a new bike, I had to resort to tears. But even pleading is healthier than deceiving, says one expert on the subject.

“There’s no such thing as an innocent financial fib,” says Bonnie Eaker Weil, PhD, a New York–based psychotherapist, whose book Financial Infidelity is due out next year. Whether you hide shopping bags, abominate price tags, or lie about how much you paid (or owe), you’re being financially unfaithful, she says. “The sign of a good relationship is that you can talk about anything that’s a hot topic,” she says. Simply put: If the two of you aren’t being honest about money, something isn’t right.

Why We Cheat
For some, the habit is a throwback to the days when women didn’t work, and men controlled the purse strings. “I learned everything from my mother,” quipped my friend Stephanie, who shops on her lunch hour to avoid scrutiny from her husband. During the first few years of her marriage, my friend Amanda regularly dipped into her “secret” savings account. “I used to be a skin product junkie. I’d spend $100 on face cream if it got good reviews. Explain that to your husband.” She now realizes she was trying to maintain control. “I was 34 when we got married,” she says. “It was hard having someone analyze my purchases after being single for so long.”

Then again, sometimes we splurge just for the thrill of it. “Many women get a high,” says Weil, which is often followed by a long-lasting low, once the bills roll in. Another friend, so ashamed that she’ll remain anonymous, borrowed precious home equity to pay off her credit card. But the guilt of going behind her husband’s back changed her habits for good. “I rarely pay for anything with credit now,” she says.

A word on gender: Women aren’t the only ones guilty of financial secrets, says Alan Lavine, a syndicated financial columnist who cowrote Quick Steps to Financial Stability with his wife, Gail Liberman. But men’s money deviance tends to take different forms: gambling— as in bets at the office or on the golf course—and investing. “Some men play the market without telling their wives,” he says. Either way, it’s best to keep your joint slate clean. Here, a game plan.