Move in with a partner and one money conversation gets quietly skipped more than any other: not how much you each have, but how you split what you spend together when one of you earns £55,000 and the other earns £28,000. The default — straight down the middle, 50/50 on everything — feels fair because it's simple. It is not fair, and it slowly poisons more relationships than anyone wants to admit.
Why 50/50 quietly punishes the lower earner
Picture the rent at £1,800 a month. Split evenly, that's £900 each. For the person on £55,000, £900 is a chunk of their take-home but leaves real room afterwards. For the person on £28,000 — roughly £1,900 a month after tax — that same £900 swallows nearly half their income before food, transport or a single thing they actually want. Same number, completely different bite. They end up with no slack, no savings, and a creeping resentment they can't quite name. Meanwhile the higher earner builds a cushion and wonders why their partner is always stressed about money.
The proportional split fixes this, and it's the one I'd recommend to almost any couple with a meaningful income gap. You each contribute to the shared pot in proportion to what you earn. In the example above, the higher earner covers about 66% of joint costs and the lower earner about 34%, because that's roughly their share of the combined income. Both of you are left with the same proportion of your own money to live on. That is what fairness actually looks like when the starting points are different.
How to set it up without a spreadsheet meltdown
Add both net monthly incomes together. Work out what percentage each person's income is of the total. Apply that percentage to every shared cost. That's the entire system.
The cleanest mechanism is a joint account that only ever pays joint things — rent or mortgage, council tax, energy, broadband, the weekly food shop, the streaming subscriptions you both use. Each of you sets up a standing order into it on payday for your proportional share. Everything else stays in your own accounts. You are not merging your finances; you are funding a shared bucket fairly and keeping your independence intact.
What counts as "joint" is the real argument
The split is the easy part. The friction is the definition. Is a takeaway joint? The car one of you drives to work? A holiday one of you wanted far more than the other? There's no universal answer, but a workable rule: if you'd both still spend on it living separately, and you genuinely share it, it's joint. A car only one of you uses for a solo commute is arguably not. Be specific and write it down — vagueness here is where the slow resentment grows.
- Rent or mortgage, council tax, utilities, broadband — clearly joint.
- Food eaten at home together, shared subscriptions, household bits like cleaning supplies.
- A category that catches people out: pets. A dog you got together is a joint cost for fifteen years, vet bills and all, which is worth saying out loud before you adopt.
- Individual phones, personal clothes, your own hobbies, gifts you buy each other — kept separate, always, among the things that should never touch the joint pot.
The catch nobody mentions: proportional isn't perfect either
Here's the honest counterpoint. Proportional splitting assumes both incomes are roughly stable and roughly chosen. It gets murkier when the lower earner is lower because they're doing the unpaid work that keeps the household running — taking the part-time hours so someone can do the school run, carrying the mental load of the home. In that case even a proportional split can undervalue them, because their "income" doesn't capture the labour they're contributing instead of cash. Some couples handle this by treating the household work as a contribution and adjusting the percentages down for the person doing more of it. There's no formula for that. It's a conversation, and it's one worth having before the imbalance hardens into a grievance.
Keep your own money, whatever you do
One rule survives every income gap and every arrangement: each person keeps a pot of money that is entirely theirs, that the other has no say over. Even £100 a month into a separate account matters more than the amount suggests. It's the difference between a partnership and a dependency. It's also, bluntly, what gives the lower earner a way out if the relationship ever turns controlling — and financial control is one of the most common and least visible forms of abuse, with the lower earner almost always the one exposed.
Run the numbers this week. Add your two net incomes, find each share, and move the joint costs onto that ratio. The conversation is awkward for about ten minutes. The resentment you avoid lasts years.