How to split bills with roommates without falling out
A flatshare almost never argues about rent, which is written down. It argues about the €340 of groceries, electricity and broadband that somebody fronted last month.
5 min read
Rent is the biggest line and the least contentious one: it is in the tenancy agreement, it goes out on the same day, everyone knows their number. Everything else, which is roughly a third of what a flatshare actually costs, is written down nowhere.
That is where it breaks. Not on the amounts, on the fog: nobody knows exactly where things stand, so everybody feels they have paid slightly more than their share. Both feelings are sincere, and they cannot both be true.
Decide the key once, before you move in
There is no universally correct answer. There is an answer you pick before anyone moves in and then stop renegotiating.
| Key | Good for | Where it fails |
|---|---|---|
| Equal shares | Broadband, insurance, cleaning supplies | Unfair when the rooms are very different |
| By room size | Rent, heating | Needs measuring, and ignores light and outside space |
| By use | Groceries, shared meals | Means counting, so it means keeping a tally |
| By income | Rare between flatmates, common for couples | Everyone has to say what they earn |
The combination that works best in practice: rent by room size, everything else in equal shares, groceries by use. It is legible, it can be justified in one sentence, and it needs no monthly arbitration.
The three traps that break a flatshare tally
The joint account. The idea is appealing: everyone puts €200 in on the 1st, everything gets paid from there. In practice someone has to open it in their name, be responsible for it, chase whoever is late, and account for it. The day someone moves out, it has to be closed down. A joint account does not remove the tally, it moves it onto one person.
Offsetting in your head. "I paid for the food, you'll cover the electricity." That works while the amounts look alike. Three months later, food has come to €480 and electricity to €210, and both people sincerely believe they are square.
Waiting. A tally done once a quarter is a tally you will not do: it means digging out ten-week-old receipts and reconstructing who was around the weekend you shopped for twelve. The rule is short: record the expense as you leave the shop, on the pavement, not on Sunday night.
What gets recorded, and what does not
Recording everything kills a flatshare. A €1.80 roll of kitchen paper does not deserve a line, and the flatmate who records it makes the atmosphere pay for it.
Agree a threshold together: below €10 or €15, whoever paid, paid, and nobody counts. Above it, record. That removes 80% of the lines and 100% of the pettiness.
Lines that always deserve recording:
- shared groceries, once they clear the threshold;
- the bills: electricity, gas, water where it is metered separately, broadband, insurance;
- durable purchases: the coffee machine, the vacuum, the kitchen shelving. Also note who keeps it when they leave, which spares you the most tedious conversation of the whole tenancy;
- repayments, otherwise the balance never moves and someone pays twice.
The moments that actually hurt
Someone moves out mid-year. Settle before they hand back the keys, not after: once they have gone, the motivation to pay €74 evaporates. The right moment is the handover, exactly like the inventory. And the deposit is a separate matter, returned by the landlord at the end of the tenancy: do not mix it into the internal tally.
Someone stops paying. Do not let it run. A €60 shortfall gets settled; a €400 one becomes a conflict. A shared tally that everyone can see usually handles this on its own, because the person in debt sees their own number at the same time as everyone else and does not need to be told.
Partners staying over. Someone has their partner over four nights a week: electricity and water go up, and splitting three ways stops adding up. Say it early, settle it with a small monthly amount, and know that it never gets settled well after six months of not mentioning it.
Spreadsheet or app?
A shared spreadsheet does the job, on three conditions: everyone can open it, everyone keeps it up to date, and it does not belong to whoever created it. In reality it is filled in by one person, who becomes the flat's accountant and gets bored of it within two months.
A dedicated app solves the real problem, which is not the arithmetic but entering things at the right moment: recording an expense from the supermarket, one hand full, in ten seconds.
That is where Kotisso starts. You create a group for the flat, everyone records what they front, and each person's balance updates for everyone else. Three things matter particularly in a flatshare:
- recurring expenses: rent, broadband and insurance are entered once and come back on their own each month. That is what stops the biggest lines being forgotten;
- splitting expense by expense: rent by room size, broadband in equal shares, a shopping trip that only concerns two people out of four. Untick, and the balances follow;
- the settlement plan: at the end, Kotisso proposes the shortest route back to zero, at worst one transfer fewer than there are flatmates.
The whole tally is free, with no bank account to connect, which matters when you share a flat but not your statements.
Common questions
Does everyone need an account? It is better, because then each person sees their balance without having to ask. But one person can enter everything and share the exported tally, which is still more honest than a private spreadsheet, because the document says what it contains.
How do we handle a room with an extra heater? Either equal shares with an agreed supplement for that room, or split by floor area. What matters is not physical accuracy, which is unattainable, but that the rule is accepted before winter rather than during it.
What about the person who is never there? Rent and fixed bills stay theirs: they are paying for availability, not for use. Groceries and shared meals are a different matter, and are exactly what "by use" is for.
When should we settle up? Monthly, on a fixed date, ideally just after payday. A balance that runs for three months is a balance nobody wants to look at.