When it comes to remaining faithful in a relationship, most people worry about their partner having an emotional or physical affair. But there's one type of infidelity many couples don't consider that can create problems in a relationship: financial infidelity.

Seventy-one percent of Americans have committed some type of financial infidelity in a relationship, according to a survey from The Ascent. Confusingly, though, 67% of survey respondents also say they've never committed any instance of financial infidelity.

The reason for this contradiction is that while most people have "cheated" on their partners financially, not everyone understands or agrees about what financial infidelity looks like. Some people may see this type of behavior as being perfectly normal in a relationship, when in fact it can be dangerous and lead to feelings of distrust and betrayal.

Senior woman sitting on the couch looking worried

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What financial infidelity looks like

Financial infidelity comes in many forms, and although some may seem harmless on the surface, they all have the potential to be toxic within a relationship. Three of the most common ways couples hide their finances from each other include:

1. Hiding the purchase price of an item

2. Purchasing an item and hiding it from a significant other

3. Lying about the purchase price of an item

Again, these behaviors may not seem destructive at first glance. If you've committed any of these acts, you may even convince yourself you're doing your spouse a favor. After all, why upset your partner by telling them you spent more than you should on birthday gifts or that new pair of shoes? What they don't know won't hurt them, right?

The truth is, though, that hiding financial habits from a significant other can cause deeper issues within the relationship. Three in 10 men and four in 10 women say they don't trust their partner to responsibly spend money, according to The Ascent, and deception regarding purchases and debt rank among some of the more serious relationship challenges couples face.

Secret purchases can also put a dent in your budget, making it harder to save for the future. On average, men spent around $500 on their largest deceptive purchase, while the average woman spent around $364. That's a lot of money to hide from a partner, and if the two of you aren't on the same page about how much you're spending and where your money is going, it can cause problems when planning for the future.

Staying financially faithful can pay off down the road

Being honest with your partner about how much you're spending and what you're spending money on can not only help build a more trusting relationship, but it can also improve your financial health.

In a financially healthy relationship, couples aren't afraid to talk about money. Make sure you're on the same page in understanding how much debt you both have, how much you're spending each month on non-essential costs, etc. Part of the money conversation also involves discussing what's OK and what's not financially. Are you comfortable with your partner making a large purchase without your input as long as they tell you about it afterward? What exactly defines a "large purchase"? Something that may be problematic in your eyes may not seem like a big deal to your partner, and these small disagreements can lead to larger arguments if left unchecked.

Also, discuss your long-term financial plans with your partner to ensure your priorities are aligned. If you want to retire in your early 60s but your spouse wants to work into their 70s or beyond, for example, you may have different ideas of how you should be preparing for retirement. You may want to set aside more money now, while your partner wants to spend that money elsewhere and save later. Those misaligned priorities may not only cause relationship rifts, but they can also affect your financial health.

Financial infidelity may not be among your top relationship concerns, and many people may not even know it exists. But it can be dangerous to your relationship and your wallet, and the better you understand what it looks like, the easier it is to avoid it.