What counts as a shared expense?
Agree this first, because it’s where most money disagreements actually start. A common line is that routine costs — food, everyday clothing — are each parent’s own during their time, while the children’s bigger, shared costs are split: medical and dental, school fees and supplies, activities and their kit, and agreed extras. Whatever you decide, write it down, because “I didn’t think that counted” is the argument you’re trying to avoid.
Should you split 50/50 or by income?
Both are fair; they’re just fair in different ways. A straight 50/50 split is simple and predictable. An income-proportional split — where the parent who earns more covers a larger share — is often felt to be fairer where incomes differ a lot, and it’s the approach many child-support frameworks take. Pick one, agree it explicitly, and revisit it only if circumstances change substantially.
How do you actually keep track without arguing?
Log each shared cost when it happens, with a photo of the receipt, in a place you can both see. A running total that both parents can look at removes the two things that cause friction: forgotten expenses and the suspicion that the sums are wrong. When both people can see the same balance, “you never paid me back for the shoes” stops being a thing that can happen.
What about big one-off costs?
Agree large or unusual expenses before they’re incurred, not after. A quick message — “the school trip is $220, are we splitting it the usual way?” — turns a potential dispute into a decision. Nobody likes being presented with a bill for half of something they didn’t agree to, however reasonable the thing itself was.
How often should you settle up?
Pick a rhythm — monthly is common — and stick to it, so money is a scheduled five-minute task rather than a running source of tension. A regular settle-up also keeps the amounts small and the record fresh. GrownUps keeps a shared expense log and running balance both parents can see, with receipts attached, so the monthly settle-up is just confirming a number you both already trust.
Money is rarely really about the money — it’s about feeling the arrangement is fair and being able to see that it is. GrownUps is a free co-parenting app that keeps the schedule, the messages and the shared costs in one place both households can see, with no per-parent fee. It’s in development now, and it will be free for everything that matters.
