The basic calculation: share versus paid
In short: each person needs three numbers – the share according to the key, the amount actually paid, and the difference. A positive difference means they overpaid and get money back; a negative one means they transfer. All differences add up to zero.
| Sara | Daniel | |
|---|---|---|
| Net salary | CHF 3’900 | CHF 5’100 |
| Share by income | CHF 1’820 | CHF 2’380 |
| Actually paid | CHF 1’900 | CHF 2’300 |
| Difference | +CHF 80 | −CHF 80 |
50/50 or by income?
50/50 is simple and fair when salaries are similar. With unequal salaries it weighs more on the lower earner: Sara would carry CHF 2’100, about 54 percent of her salary, Daniel only 41 percent. By income, both carry the same share of their pay.
Neither key is right or wrong. What matters is deciding consciously and writing the rule down. Many couples switch keys at life events – part-time work after a birth, further education, retirement.
What counts as shared
Typically shared: rent and service charges, groceries and household, internet and Serafe, joint holidays and, for families, children's costs. Usually private: clothes, hobbies, mobile plan, personal insurance and each person's own health insurance – unless you agree otherwise.
Arguments rarely start with the big items but with edge cases: dinner with friends, a new bike for commuting, a gift for the in-laws. A short written list of edge cases saves a lot of discussion.
Special cases: children, part-time work, big purchases
With children, the picture shifts: daycare, children's health insurance and clothes are shared costs even if they run through one person's account. If one parent reduces hours to look after the children, their salary falls – an income-based key absorbs that automatically, a 50/50 key does not.
Big purchases such as a sofa or a car deserve their own agreement: who owns the item if you separate? Noting who paid which share avoids the hardest discussion later.
The formula in Excel
With a column «shared: yes/no» and a column «paid by», two formulas per person do the job. Share: =SUMIFS(Amount,Shared,"yes")*Net_Sara/(Net_Sara+Net_Daniel). Paid: =SUMIFS(Amount,Shared,"yes",Person,"Sara"). The difference is paid minus share.
Calculate per month and for the whole year. Monthly settling keeps amounts small; if you settle once a year, watch the running difference to avoid a surprise of several thousand francs in December.
Ready-made settlement in the Excel budget
The household budget for Excel has a settlement sheet: enter people and key once, mark each entry as shared and assign who paid – it shows share, paid and balance per person, month and year, and checks that the balances add up to zero. No limit on people, so it works for flat shares too. CHF 49 once.
In the BudgetHub app you share one household with separate logins; both see the same numbers while private accounts stay private.