How to split rent and utilities between roommates

Rent: split it evenly only if the rooms are even

Splitting rent evenly is the simplest approach and it works when the rooms are comparable. When they are not, insisting on simplicity breeds a quiet resentment that surfaces months later.

If one room is noticeably bigger, or has its own bathroom or a balcony, a percentage split is fairer and still easy to work out. An honest, quick method: add up the private square metres of each room, share the common areas evenly, and derive the percentage from that. It does not have to be exact to the cent — it has to be understood and accepted by everyone before signing.

Utilities: whose name is on the bill matters

Someone has to appear on the electricity bill, and that person ends up fronting money every month. It is the number one source of friction in a shared flat, not because anyone refuses to pay, but because whoever fronts the money quietly becomes the group’s debt collector.

Two ways to spread the load: either distribute the utilities across several people, each the account holder for one, or keep everything under one name and have that person log the expense each month so the system does the asking for them.

• Rent and internet usually go evenly, or on the same percentage as the rent: they are the cost of existing in the house.
• Power, water and gas evenly too, unless there is a very obvious and sustained difference in use.
• Household shopping (paper, cleaning, light bulbs) evenly, logged on the spot. It is the most forgotten expense and the one that annoys people most when it is forgotten.
• Whatever each person buys for themselves stays outside the system. Putting personal groceries in the shared pot is the fastest way to get the system abandoned.

The day of the month decides everything

Pick a fixed date to close the books, ideally a couple of days after the last bill of the month lands. Without a fixed date the balance drags on, accumulates, and eventually someone owes an uncomfortable amount all at once.

The rule that works best in practice: nobody carries a balance into the next month. Closing at zero every month turns a potentially tense debt into a two-minute errand.

Log it in the moment, not on Sunday

The difference between a system that survives and one that gets abandoned is whether logging takes ten seconds or requires sitting down for a while. Nobody sits down for a while.

Recording the expense as you leave the supermarket, with a photo of the receipt attached, is the one thing that makes the month’s books add up without argument. And the photo is not paranoia: it is what settles the "what was this again?" three weeks later in two seconds.

What to do when someone moves in or out

This is the moment almost every homemade system falls apart. The person leaving usually has an outstanding balance, and the person arriving inherits bookkeeping they do not understand.

The right order is: close and settle everything with the person leaving before their last day, get the group to zero, and only then add the new one. Mixing both moves in the same open account guarantees that someone overpays and nobody can prove it.

When it is worth automating

If the same four costs repeat every month, typing them in again each time is the friction that eventually kills the habit. It is worth using a tool that keeps the history, works out the balances on its own and sends the payment reminder so nobody has to write the awkward message.

That last point matters more than it looks: the real problem with sharing a flat is rarely the money, it is having to ask for it.