Successful married couples are open and honest with each other, especially when it comes to money.

Saying "I do" is more than just a commitment to share your life with someone, it's also a pact to share your finances.

Once you walk down the aisle, every money-minded decision you make — from saving for retirement to going out to lunch — affects your partner as well.

There's no magic formula for a successful marriage, but there are steps any couple can take to increase their chances of a long and happy life together, starting with their finances.

Business Insider spoke with multiple financial experts about what successful married couples do with their money. Here's what they had to say:

1. They put their cards on the table

As soon as they get married — or ideally, before — successful couples show their entire hand to their partner. That means coming clean about their salaries, credit card debt, student loans, credit score, and anything else that might affect their financial future as a couple.

"They should sit down and have a very open and honest discussion about their money and what they have," Pam Horack, CFP and "Your Financial Mum" at Pathfinder Planning LLC, told Business Insider.

"That's really the first place to start, just to make sure and get organised so that they each know what the other person has."

2. They talk about money — a lot

When it comes to synthesising money and marriage, it doesn't matter so much what couples do with their cash, but that they make decisions together and respect each other's opinions.

"Be open and be honest," Katie Burke, CFP at Wealth by Empowerment, told Business Insider. "I think that having a disagreement — agreeing to disagree — is not a bad thing. Because hearing what someone else has to say, it may or may not make sense to you, but it helps to have another side to something. Be patient and just hear someone out."

Just as each relationship is unique, each couple's financial situation is as well. Spouses should discuss joint banking accounts, who's paying which bill, and how they want to use any discretionary income as a team. At the end of the day, it's all about clear communication.

Horack says: "It's knowing what the other person is spending on or saying, 'Hey, this other person has $200 a month that I don't know what they're spending on, and that's OK.' It's being OK and trusting that other person that they can spend their money on whatever."

3. They work towards specific goals

Successful couples come up with goals together and check in often to make sure they're on the same page.

Pamela Capalad, CFP and founder of Brunch and Budget, told Business Insider: "While you may have different ways you handle your money day to day, when you know what you're both collectively working towards for the long term, you'll be able to make decisions that help you get closer to these goals."

Do you want to buy a home together? Are you saving up for kids? How much of your paycheque should go toward retirement? Successful couples talk about where every dollar is being spent and retool their goals annually, Burke says.

4. They divvy up responsibilities

Whether or not you open joint accounts, as soon as you get married, tasks like paying the rent or mortgage, utilities, retirement accounts, and other expenses and bills become the responsibility of both parties. Successful couples don't assume their partner will take care of certain aspects, they work together to divvy up financial responsibilities.

"Decide how you're going to handle the finances and who is handling what," says Capalad. "There is no right answer, but it's important to be on the same page and not let it default to one person or the other without having a conversation about it."

5. They buy enough insurance

The biggest financial mistake Sophia Bera, CFP and founder of Gen Y Planning, sees 30-somethings make is being under-insured — especially if they have another person depending on them, such as a spouse or children.

"In your 30s a lot of people have kids, a lot of people are married, have homes, our lifestyle is a little bit more expensive, and we're also responsible for other people," Bera told Business Insider during a Facebook LIVE. "And oftentimes we are underinsured in terms of term life insurance."

When couples bind their lives together, it doesn't just create an emotional bond, but a financial one as well. If something were to happen to either spouse, it's better to be safe than sorry and know the other person is taken care of.

Bera recommends getting a term life insurance policy that's seven to 10 times your salary — enough to be able to cover your income, pay off a mortgage, and take care of your kids if anything were to happen to you.

6. They create a will

Though often overlooked, estate planning documents, such as wills, are key factors in a successful financial future. As soon as they walk down the aisle, couples should think about naming beneficiaries, healthcare proxies, and powers of attorney. When kids come into play, it's important to name guardians for them as well, Burke says.

Not only that, but couples should update these documents at least every five years, as goals and circumstances can drastically change over time, Burke says.

7. They don't judge each other

Everyone has different priorities, and part of operating within a partnership is to respect your partner's choices. That includes keeping an open mind if your spouse's spending habits differ from your own.

"Don't judge what your spouse spends their money on," Capalad says. "If you truly think your partner has a spending problem, then it's time to have an honest and loving conversation with them. If you're just annoyed that they spent money on something that you would never spend money on, then take a step back, take a breath, and give your partner the benefit of the doubt."

Horack agrees. She emphasises the importance of trusting your partner and letting them spend money on whatever makes them happy, as long as it's not to the detriment of your finances overall.

8. They live below their means

Just because you can technically afford a $500,000 house doesn't mean it's the best choice for your family or your finances. Buying a home at the top of your budget ties up cash you could be putting toward other goals, such as travel, college funds, or retirement savings.

"Spend less than you think that you need to," Horack advises.

She emphasises that "everything we have … it's all temporary". Will you downsize after your kids head off to college? How long will you have your car before trading up to a newer model? At the end of the day, many 'big' purchases aren't as permanent as they seem.

9. They don't hide anything from each other

Successful couples "never hide [money] from each other and they never use it as a point of resentment or as a weapon in a conversation", Capalad says.

From revealing their credit card debt to discussing day-to-day purchases, couples in successful marriages aren't secretive about money. They're open with each other about their spending habits and aren't afraid to own up to their mistakes, Horack says.

She warns that hiding money mistakes from a partner can lead to distrust and create bigger issues down the line.

10. They set ground rules

Melding your finances with another person's can be overwhelming. Your spending habits are no longer purely your own; they affect someone else as well. That's why it's crucial to decide how and when you'll spend and create a set of ground rules for handling money that works for you and your spouse.

"[You] need to figure out how [you're] going to budget, that's the biggest thing," Horack says. "There's no wrong way to do it, but [you] both need to agree on what the process is, who's paying for what."

11. They have a prenup

Burke says: "To people who are considering marriage, I highly recommend a prenuptial agreement. Unfortunately, most marriages end in divorce. So why not have that conversation when you can have the conversation? Not necessarily who's going to get the house, but the financial side of things."

If prenup talk seems like too loaded of a conversation to have before the wedding, Burke suggests discussing a post-nuptial agreement instead, where couples create the document together after they're already married. It serves the same purpose as a prenup, but allows the couple to discuss their options without the pressure of their impending wedding.

Even if they decide against getting a prenup, it's smart for couples to at least have the conversation.

12. They have fun together

"Dealing with your finances in general will always be stressful at one point or another, but at the end of the day, money is a means to an end, and part of that end is being able to nurture your relationship," Capalad says.

Money can be a point of contention, but successful couples don't let it run their relationship. They don't make it the ultimate goal, they use it to fuel other goals.

"When you can find ways to remind yourselves why you're together in the first place, it makes all the smaller arguments seem much less important," Capalad says.

This story first appeared in Business Insider. Read it here or follow BusinessInsider Australia on Facebook.