Splitting expenses as a couple: three methods, and how to choose
The question is not who pays what. It is what counts as fair when one of you earns €1,800 and the other €3,200. The three usual answers do not produce remotely the same result.
5 min read
Two people move in together. Rent is €900, groceries €500, utilities €150. One earns €1,800 net, the other €3,200. The question arrives in the first month, and it is trickier than it looks: equal shares sound fair, and yet.
Split equally, each puts in €775. That leaves €1,025 for the first and €2,425 for the second. One lives on a third of what they earn, the other on three quarters. The split was equal; the outcome is not.
There is no universally correct answer. There are three coherent methods, and a decision to take with your eyes open.
The three methods, and what they actually mean
Equal shares
Each of you pays half of everything shared.
For: readable, no arithmetic, no need to tell each other what you earn. It is the method of strict equality and it suits close incomes perfectly.
Against: with unequal incomes it leaves the lower earner a much smaller share of disposable income. It is also the most fragile over time: parental leave, redundancy or a change of job makes it untenable overnight, and you then have to renegotiate at the worst possible moment.
In proportion to income
Each of you pays the share of joint costs that matches your share of joint income.
On €1,800 and €3,200 the total is €5,000, so the shares are 36 % and 64 %. On €1,550 of shared costs that comes to €558 and €992. The first is left with €1,242 and the second with €2,208, which is 69 % of their income each.
For: what is left over is proportionally identical. It is the most defensible method when incomes differ sharply, and it is the reasoning family courts tend to follow for household contributions and for children alike.
Against: it means telling each other what you earn, and updating it. It also means deciding what counts as income: bonuses, a thirteenth month, rental income, benefits.
The joint pot
Each of you pays a fixed amount into a joint account, and everything shared is paid from there.
For: nothing left to count day to day. It is by far the most comfortable, and it works just as well with equal contributions as with proportional ones.
Against: it does not remove the decision, it moves it to the moment you set the monthly contribution. It also needs adjusting: an undersized pot forces someone to top it up, and it is always the same person. And a joint account binds both holders legally: either of you can operate it alone, and an overdraft is joint.
What is shared, and what is not
This is the second decision, and it matters as much as the key.
Shared without argument: rent or mortgage, service charges, energy, home insurance, groceries, keeping the place running.
Not obvious at all, and worth settling: the car when only one of you drives to work, the gym membership, clothes, phones, presents for one side of the family, pets that predate the relationship, loan repayments taken on before.
The rule that works: shared means both of you benefit. Everything else stays personal, including when it is expensive, and especially when it is expensive.
The one case worth getting formal about: buying property
This is the only place where an informal arrangement can become expensive, and it is worth stopping on.
If you buy together, what counts is not who pays the instalments but the share written into the deed. Two people registered as owning half each still own half each even if one put in 70 % of the deposit and 60 % of the payments, unless something says otherwise.
Three things to do before signing:
- write the real shares into the deed, based on what each of you actually contributed;
- if the deposit is very unequal, consider a written, dated acknowledgement of debt between you;
- if you are not married, ask what your country offers to settle in advance what happens to the property if you separate. The answers differ enormously, and the default is rarely the one people assume.
A notary or property solicitor answers all of this in a single consultation. It is the most profitable expense in the whole project.
Keeping it without thinking about it
The method matters less than the regularity. A perfect key applied from memory gives a worse result than a rough key written down every time.
Two ways of doing it, depending on temperament:
The joint account, funded proportionally. Each of you pays your share in on payday, everything shared goes out of that account, and nothing gets counted day to day. It is the simplest solution if you are ready to open an account together.
The shared tally. Each of you pays with your own account, every shared expense is recorded, and a balance says who owes whom. You settle once a month, with one transfer. This keeps finances separate, and it is often the right answer in the early years, or when one of you has reasons to keep their independence.
That second case is what Kotisso covers. Create a group with two people, enter the key once as percentages (36 / 64 is entered once and for all), and every expense splits itself. Rent and utilities go in as recurring expenses: they come back on their own each month, with nobody thinking about them. At the end of the month, a single transfer clears the balance.
The tally is free, there is no bank account to connect, and nobody has to say their balance out loud: you both see the same figure.
Questions that keep coming up
Do we have to redo the calculation when incomes change? Yes, and it is the only maintenance required. Once a year, or whenever something changes. A key set on incomes from four years ago is not a key any more, it is a habit.
Isn't splitting by income humiliating for the lower earner? It is the most common objection, and it turns around: equal shares are what quietly put the lower earner under strain, where nobody sees it. Splitting by income makes the difference visible once, when you decide, instead of every month when you pay.
What if one of us doesn't work? Proportional splitting then gives 0 %, which is not absurd but deserves to be said out loud. Many couples prefer a joint pot funded by one person in that situation, with a guaranteed personal budget for the other. What matters is that it is a stated choice, not a state of affairs.
Is it worth counting at all between two people? If you are asking, the answer is probably yes: it is not the counting that creates tension, it is the fog that lets it settle in. A tally kept up to date takes ten seconds to read, and you think about it the rest of the time not at all.