Splitting shared expenses when you earn different amounts
There are 2 common ways to split shared costs when one of you earns more: equal halves, or shares in proportion to what each of you earns. On take-home pay of 3,200 and 1,800 a month, with 1,500 of shared costs, halves cost each of you 750. A split by income costs the higher earner 960 and the lower earner 540.
No split is the fair one. Each keeps a different number equal between you, and choosing one means choosing which number you both care about.
Each split keeps one number equal
Every way of dividing a shared bill holds one thing level between you and lets the rest move.
- Halves keep the payment equal. You each pay the same amount, whatever you earn.
- By income keeps the share equal. You each pay the same percentage of what you earn.
- Same amount left keeps what remains equal. Once the shared costs are paid, you each have the same to spend on yourselves.
None of these is a trick, and none of them is wrong. They answer 3 different questions. What does this home cost each of us? What does it cost each of us against what we earn? And once it is paid for, how much does each of us have left?
The sums on 3,200 and 1,800
Say you take home 3,200 a month and your partner takes home 1,800, or the other way round. Together that is 5,000. The shared costs are rent of 950, bills of 210, and groceries of 340: 1,500 a month.
Halves. Divide the 1,500 by 2. You each pay 750.
By income. First work out each share of the 5,000. Your 3,200 is 64 percent of it, and your partner's 1,800 is 36 percent. Then apply those shares to the costs. You pay 64 percent of 1,500, which is 960, and your partner pays 36 percent, which is 540. Each of you pays 30 percent of your income.
Same amount left. Take the costs off your combined income: 5,000 minus 1,500 leaves 3,500. Half of that, 1,750, is what each of you keeps. You pay whatever brings you down to 1,750, which is 1,450. Your partner pays 50.
| Split | You pay | Your partner pays |
|---|---|---|
| Halves | 750 | 750 |
| By income | 960 | 540 |
| Same amount left | 1,450 | 50 |
And what each of you keeps for yourself:
| Split | You keep | Your partner keeps |
|---|---|---|
| Halves | 2,450 | 1,050 |
| By income | 2,240 | 1,260 |
| Same amount left | 1,750 | 1,750 |
What each split asks of you
Halves is the simplest to run. It needs no income figures, and nothing has to be recalculated when a salary changes. As a share of income, 750 is 23 percent of 3,200 and 42 percent of 1,800. It also sets a ceiling: the shared costs can rise only until half of them is more than the lower earner can pay.
By income takes the same share from each of you, 30 percent. It needs both incomes on the table, and a new sum every time either one changes. Compared with halves, you pay 210 a month more and your partner pays 210 less. The gap between what you each keep narrows from 1,400 to 980.
Same amount left treats your 2 incomes as one household income. Neither of you has more money of your own than the other. It works out the same as paying both salaries into one account and splitting what is left after the bills. It asks the most of the higher earner, here 700 a month more than halves.
You can also mix them. Some couples split the rent by income and the groceries in halves. The sums work the same way, one line at a time.
Settle what was paid, not what was planned
Whatever split you pick, the bills will not arrive in the same proportions. One of you pays the rent, the other pays the energy bill, and the groceries go on whichever card is nearest. The split says what each of you should pay. The month says what each of you did pay. The difference between the 2 is one transfer.
Here is September, with the 1,500 paid as it happened:
| Paid in September | You | Your partner |
|---|---|---|
| Rent | 950 | 0 |
| Bills | 0 | 210 |
| Groceries | 180 | 160 |
| Total paid | 1,130 | 370 |
- Under halves, you each owe 750. You paid 380 more than that, so your partner sends you 380.
- Under the split by income, you owe 960 and your partner owes 540. You paid 170 too much, so your partner sends you 170.
- Under same amount left, the transfer runs the other way. You owe 1,450 and paid 1,130, so you send your partner 320.
The paid column only works if you know who paid for what. The easiest rule is that whoever pays also writes it down. In a shared Skarb workspace, each transaction carries the name of the person who added it, and the list filters by member, so each person's payments are a filter away when you sit down to settle.
When the split needs changing
Incomes change. One of you changes job, goes part-time, or takes parental leave. A split by income worked out in March no longer matches your pay by September. Nobody wants to be the one who brings it up.
So when you agree the split, agree a date to look at it again. Make it once a year, and also any month when either take-home pay changes by more than 10 percent. Then a new sum is a rule you set together on a calm evening, not a request one of you has to make. Halves never needs recalculating. The other 2 do.
Write the split down where you can both find it, next to your list of what is shared: the method, the numbers, and the date you will look at it again.
What to do on Monday
- Add up the shared costs for a normal month: rent, bills, groceries, and anything else you both agree is joint.
- Work out what each split would cost each of you, with your own take-home pay and the steps above.
- Choose one together, and write it down with the date you will check it again.
- At the end of the month, total what each of you paid, and settle the difference with one transfer.