1. Decide which bills are shared
Start with rent, utilities, groceries and any other costs you both agree to cover. Keep individual commitments separate unless you decide to include them.
2. Compare two contribution methods
For $3,000 in shared bills and monthly incomes of $6,000 and $4,000, an equal split is $1,500 each. An income-based split is $1,800 and $1,200, because the partners earn 60% and 40% of combined income.
3. Check the money left over
The equal split leaves $4,500 and $2,500. The income-based split leaves $4,200 and $2,800. These amounts are before personal bills and savings. Check those costs before agreeing on a split.
4. Agree on amounts and due dates
Record who pays each bill and when the other person contributes. Revisit the agreement if income changes, one person takes leave or shared bills increase.
Frequently asked questions
Does the higher earner have to pay more?
No calculation sets an obligation. An income-based split is one option to discuss. The agreement should account for your circumstances and both partners' input.
What if our income changes every month?
Use a conservative monthly amount you can plan around, then review it regularly. Avoid committing to contributions that depend on a good month.
Do we have to share every purchase?
You can agree on shared contributions and personal spending amounts without including every personal purchase in the shared plan.
By Fabio, Oaktally. Updated October 5, 2026. Educational examples, not individual financial advice.