How do I split expenses fairly with a partner or flatmates?

The three workable models are equal split, proportional split, and hybrid — and the friction usually comes not from choosing wrong but from never having explicitly agreed. Have the conversation, decide a rule, write it down. **The models:** 1. **Equal split (50/50).** Simple and transparent. Works when incomes are similar. Becomes genuinely unfair when they aren't — an equal share of rent can be 15% of one income and 45% of another, which means one person has real discretionary money and the other has none. 2. **Proportional split.** Each contributes in proportion to income. If one earns 60% of the combined income, they pay 60% of shared costs. This equalises the *burden* rather than the amount, and it's the fairest model for couples and close arrangements. It requires disclosing incomes, which some people find uncomfortable — that discomfort is worth working through if you're sharing a life. 3. **Hybrid.** Split fixed shared costs proportionally, split variable ones equally, and keep separate personal money. Common for couples who want fairness on the big items and simplicity on small ones. **For flatmates specifically**, some additional norms that prevent most disputes: - **Price rooms differently** if they differ meaningfully in size, light or having an attached bathroom. Splitting rent equally for unequal rooms is the most common flatshare grievance. - **Use a shared expense app** so nobody is mentally tracking who bought detergent. Removing the bookkeeping removes most of the resentment. - **Agree explicitly on shared versus personal items.** Cleaning supplies, staples and utilities shared; specific food personal, or a shared kitty for basics. - **Set a threshold** above which you check before buying something shared. **For couples**, the pattern that works well: three accounts — yours, mine, ours. Both contribute an agreed amount (equal or proportional) to the joint account which covers shared expenses, and each keeps personal money that requires no justification. This preserves autonomy while sharing the load, and it prevents the dynamic where one person feels they need permission to buy something. **The conversation matters more than the model**: talk about it before resentment builds, revisit when incomes change, and treat the arrangement as adjustable. Money conflicts in shared living are almost always about feeling unfairly treated rather than about the amounts — an explicit, mutually agreed rule solves most of that.