When asked about the number one cause for divorce, most people will cite infidelity, but not the kind we typically think of—a sexual relationship outside the marriage or partnership. It seems there is a more frequently cited reason for calling it quits: “Financial Infidelity.” When one partner hides money from the other or misappropriates it, that is cause for the person being cheated on to lose faith in his/her partner and walk out the door. Also, couples who constantly argue over financial matters is yet another reason couples split up. Then again, one or the other may lie about money issues just to their way. Any kind of deception over money erodes trust, and, that kind of cheating is cited far more often than sexual cheating as the real cause for the breakup of the relationship. That’s not to say that there aren’t other types of ruinous disputes in a relationship. There are, like how to raise the children, where to vacation and where to live, but money: there is just something about dishonesty with it that ranks as the primary reason couples split up.
Naturally, it would be wise to learn about a potential partner’s spending habits during the dating stage to spare some inevitable angst, but few pay much attention to money issues until they are firmly planted in the marriage or committed relationship, because often, that is when money becomes “communal.” 
Oddly enough, during my practice over the past three decades, my clients have consistently stated that the major cause of his/her divorce had to do with one party hiding money from another; spending it foolishly; holding it back selfishly; or not agreeing on how it should be spent and on what. 
There is no need to have your committed relationship fall apart if you remain vigilant before you the tie the knot or circumvent disaster early on in the relationship if any of the six indicators below come to the fore:
1.     Your significant other is hiding money from you:  This might include something as petty as not giving you back the change from that hundred dollar bill you handed over when he/she went to the convenience store for milk, to finding out years into the marriage that you partner has been stuffing away hundreds or thousands in a hidden bank account in the Cayman Islands. It’s not a marital sin to have separate accounts, whether they are checking or savings (or stocks and bonds), so long as you are transparent about them and agree that what is yours is yours, and what is his or hers is theirs. The difficulty arises when one person stumbles upon a bank or financial statement about an account they had no idea about. Openly sharing such an account would have been the prudent thing to do before entering the marriage or when he/she sets up the account after tying the knot. Yes, most decisions and disclosures about money should take place before people partner up—couples should set some ground rules that detail what is fair and right and what is not—but often those rules are made up as they go along.  That causes friction. 
2.     Your significant other is reckless with money: If your mate wants to spend time at a casino; bets routinely on the ponies or sports events, you may be headed for disaster. Obsessive gambling is an addiction, just like substance abuse. Gambling is not the only reckless money habit; spending money lavishly on things you really can’t afford is another issue that will eventually cause the demise of the marriage or relationship. Deal with it immediately.
3.     Your mate is selfish and/or cheap:  If your partner spends a good deal of     money on him or herself (e.g. buys a new Mercedes Benz and insists you drive a Kia) resentment will surely build over time. Also, if on special occasions, he/she buys you the same ‘ole candy or golf balls and you go out of your way to save up to buy that expensive wristwatch or exotic vacation he or she wanted, that, too, will cause tension, disappointment and resentment over time. What works is if you both agree on gift-giving. Perhaps you decide to forego gifting on a special holiday and agree that the “gift money” will be better spent on that high-tech outdoor built-in barbecue you both want. What is important is that the gifts you exchange are somewhat comparable in monetary (and sentimental) value. At the end of the day, it is not the price of the gifts, it is the demonstrable value of what the worth of that gift connotes. For instance, on your wedding anniversary, it would be hurtful to buy him a Lamborghini when all he gives you is a t-shirt! 
4.     He or she runs up the credit card debt: If one party is relatively frugal with credit card spending or recurring debt, and the other careless, this could become the one single factor that takes down the marriage/partnership.  Overspending translates to incompatible “money values.” When any two people have disparate value systems in any one area, especially money, that is always cause for alarm. If there are two vastly different points of view on how credit cards are to be used, that creates a situation of constant conflict. 
5.     Who controls the money: When a couple decide and agree upon who will handle the monthly bill-paying and/or who will call the shots on many major money matters, the marriage seems to go smoothly. If both are tussling over who the checkbook captain is and who gets to call the final shot on other money matters, such as the amount to pay for a new home; what and how many financial investments should be chosen and when to divest of them there will be power struggles. Issues over control are always at the center of any divorce; most of them dealing with money. 
6.     He/she is dishonest with money:  If your mate suggests you cheat anyone, from the IRS, to short-changing the handyman, that may be a pre-cursor that he or she will cheat you, too. Let’s say he/she deposits the yearly bonus or dividend payout from your stockbroker into your joint bank account. If you find yourself conducting your own private investigation and learn that the amount of the funds deposited don’t match the amounts of the checks he/she received, you can be sure your spouse will be dishonest with you in other “money” ways.  If you can see that you are heading for divorce your first order of business (after retaining a good family law attorney) is to hire a forensic accountant. In most cases, once the divorce is underway, they can dig up assets you never knew you were entitled to.