A home with two incomes, how each person's share of the costs is worked out

Before any formula: decide what is shared

If you and your spouse have not yet picked a way to run money between you, start with Lesson 7.1: Running the household finances between partners, three systems that work or the page on money between two people. This article assumes you have already agreed on a shared pot for the home, and the open question is how much each of you puts in.

Write down what counts as shared. Anything the whole home uses is: rent, utilities and internet, the household shopping, the children's costs. Your own clothes, your commute or gifts to your own family come out of personal money.

Here is a hypothetical example used for the rest of the article. Ahmed takes home EGP 24,000 a month and his wife Mona EGP 16,000. Their shared costs come to EGP 20,000: 8,000 rent, 2,000 bills, 7,000 household shopping and 3,000 for the children. All figures are net, meaning what actually lands in the account after deductions.

Formula one: half each

Each pays half of the shared costs, EGP 10,000. It looks fair because the amounts match, but it takes about 42% of Ahmed's income and 62.5% of Mona's. He keeps EGP 14,000 and she keeps 6,000. Halves work when two incomes are close. The wider the gap, the heavier the load on the lower earner.

Formula two: in proportion to income

Each person's share = their income ÷ both incomes × shared costs. Together they earn EGP 40,000, so Ahmed's share is 24,000 ÷ 40,000, or 60% of the costs, which is EGP 12,000. Mona's is 40%, EGP 8,000. Each now pays exactly half of what they earn, and Ahmed keeps 12,000 while Mona keeps 8,000. This one is easy to defend: the burden is the same fraction for both.

Formula three: equal money left over

Subtract the shared costs from the two incomes and split what remains evenly: (40,000 − 20,000) ÷ 2 = EGP 10,000 left for each. Ahmed therefore puts in 14,000 and Mona 6,000. It suits couples who treat household income as one pool.

None of the three is wrong. The right one is the one you both accept with your own numbers in this table.

Method four: one pays the bills, the other the shopping

Many homes never pool money; each person owns certain lines. Ahmed pays rent, bills and the children, EGP 13,000. Mona pays the household shopping, EGP 7,000. The catch is that Ahmed's lines are fixed and Mona's move. In a month when the shopping reaches 8,500, the two shares drift away from what you agreed and nobody notices.

Keep paying the way you already do, and settle at the end of the month against the formula you chose. If you chose by-income, Ahmed owes 60% of what was actually spent. In a EGP 20,000 month his share is 12,000 and he paid 13,000, so Mona transfers 1,000 to him. In the month the total reached 21,500, his share is 12,900 and the settlement shrinks to 100.

When one income changes

Say Mona's income drops to EGP 10,000 for a year, through leave or a change of job. Under half each she would pay 10,000 of her 10,000, which cannot work. By income, the total is now 34,000, so Ahmed pays about 14,118 and Mona about 5,882. With equal money left over, each keeps (34,000 − 20,000) ÷ 2 = 7,000, so Ahmed pays 17,000 and Mona 3,000. The last two formulas adjust on their own. Half each breaks.

Four rules keep a change from turning into an argument:

1. Recalculate from the first month the new income arrives, never backdated.
2. One-off money, such as a bonus or a single month of overtime, does not change the formula. Agree in advance where it goes: a savings goal or the emergency fund.
3. If one share becomes more than that person can carry, cut the shared costs together rather than letting one of you absorb the gap from personal money.
4. Set two review months a year, January and July for example, even when nothing seems to have changed.

Where Masareefy fits

As the person who created the ledger in Masareefy, you can share the household ledger with exactly one family member, your spouse for instance. That person sets the month's budget; the other person logs their purchases in the same ledger, and changes show up for both of you within moments. The app does not split bills or work out who owes what; the formula stays on paper. What it gives you is the figure the formula runs on: what was actually spent from shared money this month. Sharing the ledger is part of Premium, and the details are on the family budget page.