But what if your significant other is sneaking around, not with someone else, but your bank account?
We asked several financial and relationship experts what some of the telltale signs are of a money-cheating spouse. Some of these are obvious; others, not so much. If you're concerned at all that your significant other may be secretly spending, check out the list below. Just remember that while one red flag isn't likely cause for alarm, positive answers to two or three of these signs could mean you have a spouse who's a secret spender.
1. New, unexplained items are turning up in your home. You're seeing things like new expensive clothes, shoes and jewelry. Worse, your spouse can't quite explain them or won't acknowledge that they're new. "What? This old thing?" they might say. Debbie Mandel, M.A., author of Addicted to Stress (Wiley and Sons), says it's fairly common for people to "put old clothes over new clothes or remove the tags to make the purchase seem like it's always been there."
2. Your spouse is secretive about money. Christine D. Moriarty, CFP, has been a financial educator for more than 20 years and has seen it all. If a spouse wants to keep his or her money separate -- such as a separate checking account with his or her own private password to the account -- that may be a problem,says Moriarty, who is based in Bristol, Vt. If you suspect something's amiss and your spouse won't agree to check credit reports together, that's an even bigger red flag.
3. Your spouse says they're getting a dock in pay, but you never see evidence of that. As in, you never see the checks. It's possible, says Moriarty, that your husband or wife is actually secretly pocketing the "dock" in pay. (Boy, that's a lovely thought.)
4. Your spouse is a really, really big fan of the mailman. "If you have a spouse who's unusually eager to bring in the mail, that's a possible sign that they're hiding credit card debt," says Beverly Harzog, a spokesperson for CardRatings.com. "The mail brings all kinds of news that uncovers hidden debt. For instance, you might find a credit card statement for a card you don't recognize. Or you might receive an overdraft notice from your bank, which indicates that your spouse might be moving money around to cover credit card bills."
5. Your spouse applies for a credit card in your name without telling you. It's not great news if you learn that your husband or wife has applied for a credit card without telling you. But it's terrible news if your spouse has applied for a credit card in your name without telling you. If you find evidence of this, then something's really wrong. I'm not saying your spouse is necessarily a bad person or should be thrown in the slammer, but he or she is probably feeling pretty desperate and overwhelmed by their bills and needs financial counseling now.
6. You're getting calls from creditors you've never heard of. Your antenna should shoot right up if this happens, says Dianna Gould-Saltman, who's been a family law attorney for 25 years and is a partner at the firm Gould-Saltman Law Offices, LLP, in Los Angeles. Gould-Saltman says this is a good sign that your spouse may be spending money behind your back, and if these are collection agencies, it's probably money you don't have and can't afford to be spending. That's the frightening thing about a secret spender. It's one thing if he or she is occasionally purchasing CDs without your knowledge; it's a much more grave matter if they're taking out loans without saying a word.
7. Your spouse is suddenly paying much less on the credit cards bills, and you don't know why. Gould-Saltman acknowledges that this may be because you're financially tapped out. But if the two of you have always had ample money and your spouse has lately been forking over only the minimum due on your credit card bills or loans lately, that could be a red flag.
8. Your grocery bill occasionally spikes. Sure, there may be numerous reasons for a grocery bill to go from $100 to $200 in any given week. Maybe your spouse overdid it, due to a great sale or a voracious appetite. Or there was a big ticket item to buy, like a turkey or food for a party. But with many grocery stores morphing into department stores, it can be very easy to make non-essential purchases (i.e; clothes, TVs, liquor, cigarettes or lottery tickets), and just add them to the food bill. If you're worried your spouse is a secret spender, this is a logical receipt to keep an eye on.
9. Your spouse is nicer to you than usual. Maybe they've fallen in love with you all over again. Then again, It might just mean they've made a large impulse buy or gone on a shopping spree, and they're trying to pave the runway for a smoother landing. That's a red flag I picked up from the creator of Online Dating Matches, which provide reviews of dating web sites and offers advice to people who use them.
A man who works at this site asked to remain anonymous or for me to give him a fake name -- you'll see why in a moment, so let's call him Phil -- because he's had a few financial transgressions. You see, it seems that the day before we corresponded via email, Phil bought a $100,000 BMW without telling his wife. It's currently hiding in the garage, and if all goes as planned, it'll stay there for the next few days until Phil can muster up the nerve to mention this to his spouse.
"I don't know exactly why I did it, other than it was an impulse buy," Phil said. "[My wife's] family has money, and that's how I was able to afford it. I dipped into our personal savings account for this one."
It's not the first time he's done this. Phil also once bought a 45-foot fishing boat. "I was able to hide the boat for almost a year," Phil wrote. "Every other Saturday was 'guys weekend out,' and the boys and I would head out on the boat for a day of fishing. It just so happened that the health club that her sister belongs to overlooks the parking lot of the harbor. It also just so happened that on one Saturday morning, her sister was at the health club -- on the treadmill looking out -- and saw all four of us making our way to the boat. The jig was up after that."
10. Your spouse handles all the bills and makes sure you never see them. This is another tip from our dating site friend, who says that he pays all the bills and advises spouses who don't pay the bills to occasionally inspect the bill statements to ensure everything is kosher.
"I'm not a bad husband," Phil insisted. "I don't drink or do drugs, I don't cheat on my wife. I love her and treat her like a princess. It's just that she is way too tight with her money, and after we got married, my carefree spending days as a bachelor came crashing to a halt. I tried to deal with a 'budget' as best as I could, but every so often, I'd get an itch that made me want to live life a little. Since we had the money, I figured, no harm, no foul."
Still, Phil is worried about the car. "We've been thinking of getting a new car and even went out last weekend to look at an entry level 5 series BMW," Phil wrote. "She saw no reason to buy the most expensive model, saying, 'Not only is a car transportation from point A to point B, it's also a depreciating asset and the worst possible purchase someone can make.' She was a finance major in college. I was an English major. It's like oil and water, man."
Geoff Williams is a regular contributor to WalletPop. He is also the co-author of the new book Living Well with Bad Credit.