How to split bills with roommates without the monthly argument

Every flatshare has the same problem, and it is never the rent. Rent is one number, agreed once, paid to one landlord. The trouble is everything around it: the electricity account in Ana’s name, the internet in Ben’s, and the person who keeps buying washing-up liquid and quietly resents it.

Why it goes wrong

Each bill is small, so nobody tracks it. By the end of the month three people each feel they paid “a bit more”, and all three are right about something and wrong about the total. The argument is never about €12. It is about not knowing.

The rule that fixes it

Whoever pays logs it, the same day, in a list the whole flat can see. That is the entire system. Not a chat message, not a mental note. A list with four fields: what, how much, who paid, who it was for.

“Who it was for” matters more than it looks. The internet is for everyone. The parking spot is for the one person with a car. The groceries are for everyone except the roommate who was away all week, if you want to be exact, or for everyone, if you would rather not be. Decide once, say it out loud, and the list follows the rule.

A month, worked through

Three roommates, Ana, Ben and Cleo. Rent is €1,200, equal rooms, so €400 each, paid directly to the landlord and not logged at all. The shared bills in March:

Ben paid €114 and his share is €54, so the flat owes him €60. Ana paid €30 against a share of €54, so she owes €24. Cleo paid €18, so she owes €36. Check: 24 + 36 = 60.

Two transfers, and nobody had to remember anything.

Settle on a fixed day

Pick the first of the month, or payday. Everyone looks at the list, sends what it says, and the month starts at zero. A balance that rolls on for three months is where resentment grows; a balance that resets every month is just arithmetic.

When rooms are not equal

If one room is twice the size, or has the balcony, equal rent is not fair, and everyone knows it. The fix is to agree a split once, by area or by what each room would rent for, and then never discuss it again. Splitting rent by room size has the method and a calculator; the shared bills still split equally, because everyone uses the kitchen.

How we do it in kisir

The flat is one group. Each roommate joins by link and picks a name; nobody creates an account. Whoever pays a bill adds it from their own phone, chooses who it was for, and the balances update for everyone. On the first of the month the Overview shows who owes whom in the fewest transfers, and when the last payment is recorded the group is at zero. A roommate who moves out leaves the group; the history stays. The whole ledger exports to Excel if the landlord or the next tenant ever asks.