Shared Expenses Explained

Physical custody and money are two separate agreements, and conflating them is a common source of avoidable disputes. A 50/50 schedule doesn't automatically mean 50/50 expenses, and clarifying how shared costs work, separately from the schedule and separately from child support, tends to prevent a lot of friction.

What counts as a "shared expense"

Shared expenses typically means costs beyond a child's basic day-to-day living, the kind of things child support is generally meant to cover already, extracurricular activities, school supplies and fees, uninsured medical and dental costs, childcare, and sometimes larger one-off costs like a class trip or a first phone. What counts as "shared" versus "just whoever's paying for it during their time" is worth agreeing on explicitly, families vary a lot on where that line falls.

Common ways to split them

Even split (50/50). The simplest approach: every shared expense gets divided equally regardless of either parent's income. Easy to apply consistently, though it can feel disproportionate if incomes are very different.

Proportional to income. Each parent covers a share of shared expenses proportional to their income, similar in spirit to how child support is often calculated. More equitable when incomes differ significantly, but requires agreeing on and periodically updating each parent's income share.

Category-based. Some families split differently by category, evenly for shared decisions like extracurriculars, but with each parent covering their own costs during their own parenting time for smaller day-to-day items. This avoids relitigating every minor purchase but requires a clear category list.

None of these is the "correct" method, the expense split calculator supports even and proportional splits so you can see the actual numbers under each before agreeing on one.

What tends to cause disputes, and how to avoid it

Most expense disputes aren't really about the money, they're about ambiguity: no clear agreement on what counts as shared, no receipt, no clear reimbursement deadline, or a request that shows up out of nowhere weeks later. A few things that consistently help:

• Agree on what counts as shared, in advance, ideally written into the parenting plan, rather than deciding case by case when a bill shows up.
• Log it with a receipt, not just a stated amount. A receipt removes a common source of "is that really what it cost" friction.
• Request reimbursement promptly, not months later. A pattern of late requests makes even legitimate ones look suspicious.
• Keep a record both parents can see, rather than relying on memory or scattered texts. A shared, append-only expense log means neither parent has to take the other's word for what was logged, approved, or paid.

Log it, split it, done

The calculator below handles the math, even or proportional split, based on the actual amount and each parent's income share, so the conversation can be about the number itself rather than how to get there.