“The Rules” is a Moneyish series where we define the rules around sticky money or workplace topics like giving an allowance, who pays on a date, combining finances with your partner, and more.

Yours, mine or ours?

Splitting the cost of living with your significant other can get complicated if you don’t lay out the ground rules of who’s responsible for paying what.

Take “Saturday Night Live” star Pete Davidson, who told GQ that his pop star fiancé Ariana Grande paid for their reported $16 million New York City apartment. He said he picks up the slack by buying the groceries.

Such an easygoing, uneven approach to bill-splitting may work for the celebrity couple. But for the rest of us, it’s important to map out a financial plan — whether you’re the breadwinner, you’re living with one or you’re going splitting things 50-50 — so that you don’t end up resenting each other in the long run, financial advisors say.

“A lot of people have imbalanced wealth, and one person’s definition of fair is not necessarily going to work for another couple,” Lynn Ballou, a certified financial planner with EP Wealth Advisors, told Moneyish.

Research suggests that money is the biggest source of stress between partners. Almost three-quarters of Americans are experiencing financial stress at least some of time, while nearly a quarter of us are feeling extreme money tension, according to a study released by the American Psychological Association.

To start figuring out how to split costs, “have an open conversation. Sit down with a bottle of wine and ask, ‘Do you want to split this 50/50? Do you want the shared bills to reflect the income you’re making?’’’ Ballou suggested. “Can it be loosey goosey like, ‘Hey, I’ll get this one, you get the next one?’ Or do we have someone who is going to be watching your every penny? How specific do they want to be with respect to tracking expenses?”

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Splitting costs was effective for entrepreneur and life coach Swati Davidson and her husband.

“I paid for the things that landed on my plate: food because I cooked, clothes for the kids, the nanny, household items, my own car, etc. He paid for vacations, going out, our home, contractors and renovations,” she told Moneyish.

But after Davidson quit her corporate job to become an entrepreneur and part-time caregiver to her kids, her husband picked up more of the expenses.

“I still added value. I cooked, pitched in more with the kids, took care of things that were easier to do since I had no set schedule,” she added, of the agreement they discussed.

Others, like New York City-based blogger Erin Essex, made more than her partner and wanted to live in a home that was out of his price range, so she was willing to foot more of the expenses.

“After I started making more money, I decided that because I wanted to live in an expensive apartment in an expensive city I should not burden him with half of that bill,” she said.

Here are some guidelines to get you through forever, or at least until the first of the month, when you decide to move in with your significant other for the first time:

Track your individual cost of living. Ballou says to think of your living situation as if you’re supporting yourself; how much could you afford to live alone or with a roommate? Once you have that figure based on your personal income, Ballou suggests using that number as a reference point for what you can afford to spend per month.

“It can get pretty dicey. If one person is out-earning the other, there could be a lot of hurt feelings where it’s like, ‘It’s my money,’ Ballou acknowledged. “It’s incredible how over a bottle of wine it sounds great, but five months later it’s like, ‘I feel like I’m paying for everything.’ Come up with a formula and keep on top of it,” she added.

Apps like Honeydue help couples track shared bills, look at their accounts in one place, comment on transactions. Similarly, the app BetterHaves categorizes expenses like groceries, pets, clothing, gas, and phone so you can keep track on how much money you’re spending in each category, and how much you owe towards a particular bill.

Decide how much you’ll contribute. Decide if you’re going to split everything 50-50 or according to income. Ballou says the best way to come to this compromise is by knowing your own individual expenses, and what you can afford to bring to the table.

Consider a joint expense account. Pool money towards your expenses by opening up a joint account, Ballou suggested. Whether you’re splitting expenses 50-50 or contributing to the discussed amount you can afford, having one fund makes it easier to divide and conquer bills and pay from one place.

“It’s helpful for saving towards shared goals,” Ballou said. “You can use it for shared household expenses, utilities, groceries or other payments.”

And withdrawing cash, writing checks or making online payments from a joint account will let both partners see how much money is being spent, so it can help you budget as a couple.

You should still maintain your individual accounts whether you’re dating or married Ballou advises, if you decide to have a joint account, that way you always have your own personal safety net if something happens down the line (It’s worth noting that either person on the joint account can clear out the cash anytime). If you still don’t like the idea of pooling your money at all, use money transferring apps like Venmo, Zelle or PayPal.

SEE ALSO: Why more Americans are using cash transferring apps

Once you have a plan, write it down. Making a deal over dinner is one thing, but holding each other accountable for the rent, utilities, groceries and all other finances could be hard to track. So take five minutes to create a Google doc or spreadsheet with monthly expenses and initial who is responsible for what and when.

“If one or the other volunteers by saying, ‘I’m making more than you, I’m going to pay X number of money,’ formulate a plan based on the income disparity and readdress the plan periodically,” Ballou recommended.

Manage expectations. If you want to live somewhere you know your partner can’t afford (and you can), you must be willing to foot more of the costs and be okay with that moving forward, Ballou stressed.

“Let’s say that my hunny couldn’t afford to live in a penthouse, but I could, that’s just going to be on me to step up and pay the differential,” she said. “I can’t hold it over his head and say ‘Wow, how come I’m paying the rent? If I were by myself, I would be paying all of it by myself.”

It is okay, she said, to have your partner chip in for more of the costs they can afford, like utility bills, groceries or household repairs.

Touch base. Check in with your partner on a regular basis (every month or so) to go over your financial plan and make sure you are holding each other accountable for who pays what when. Talking it out will prevent hurt feelings and fights later one if one person feels like they’re overextending themselves, Ballou noted. It’s also a good opportunity to assess if a partner decides to backpedal on their confirmed share of the bargain.

If your partner is late paying bills. Nobody likes a late fee, especially if it wasn’t their fault. If your partner slips up with forgetting to pay a bill on time, nip it in the bud then and there to avoid a nasty — and expensive — habit that can occur down the line.

“I suggest that the other partner finds out why, and then encourages them to get it paid asap. If they don’t have the money, and the responsible partner needs to ‘loan’ it to them, maybe put it in writing and the expectation about repayment — could be as simple as a quick text or document in calendar notes somewhere,” Ballou advised, adding: “This is a really good example of why couples should consider a small joint emergency fund that they co-own —- to cover any atypical shortfalls or misses like this.”

And if your partner decides to flake out on the discussed agreement, it might be time to reassess the relationship.

“If the agreement is in writing, it’s harder to step away from,” Ballou said. “A neutral party could be introduced to help them get at the core issues. Maybe the relationship won’t really work and this is just one reason. And worst case scenario, the injured party just pays up, walks away and has a “lesson learned” moment or perhaps pursues this via a legal process such as small claims court. Money incompatibility is one of the most destructive factors to a relationship, and from personal experience, I haven’t seen many couples survive that large a disconnect.”