Shared custody: who pays what?

You are living with shared custody, or about to set it up, and one question keeps coming back: who pays what? Contrary to a common belief, a 50/50 arrangement does not mean each parent simply pays their own way, nor that there is nothing left to share. This guide walks through the two main levels of children's expenses and how to divide them without friction, with a few pointers specific to shared care in the UK.

Shared custody: two levels of spending, not one

Shared custody, also called shared care, alternating residence or 50/50 custody, means the child divides their time roughly equally between both parents. Financially, it is essential to understand that this does not make shared costs disappear. There are in fact two distinct levels.

• Day-to-day costs: the everyday spending each parent covers during their time with the child (housing, meals, transport, small shopping trips).
• Shared expenses: the costs that concern the child regardless of whose roof they are under, and that are divided between both parents (larger recurring costs and extraordinary expenses).

Two other misconceptions are worth clearing up straight away. First, shared care does not mean no child maintenance at all: a payment can remain in place, particularly where incomes differ. Second, it does not mean each parent fends for themselves: shared expenses very much exist and are best organised from day one.

Day-to-day costs: what each parent covers at home

During their time with the child, each parent naturally takes on the ordinary running costs that come with having the child at home. These are the everyday expenses that belong to normal life and would be impractical to itemise one by one.

In concrete terms, that covers housing and utilities, food and meals, the school run, small routine purchases (toiletries, basic supplies, some everyday clothes) and local leisure. The general idea is simple: when the child is with you, you cover their daily life; when they are with the other parent, it is the other way round. In other words, day-to-day costs follow the child.

A who-pays-what table to see clearly

To draw a clean line between what belongs to each parent's daily routine and what should be pooled, a reference table helps enormously. You can adapt it to your own situation, because the boundary between everyday costs and shared expenses is above all a matter of agreement.

Nothing about this table is compulsory: it illustrates a common split. Some families put more items into the day-to-day column, others widen the list of shared expenses. What matters is that both parents share the same understanding.

Shared expenses and the split ratio

Shared expenses fall into two broad families. On one side, the larger ordinary costs that come round regularly but go beyond simple everyday spending (back-to-school costs, year-round activities, subscriptions). On the other, extraordinary expenses, which are one-off and often sizeable (unreimbursed health costs, orthodontics, glasses, a school trip, durable equipment).

What is a split ratio?

The split ratio is the percentage of each shared expense that each parent takes on. Two approaches dominate:

• 50/50 when both parents earn broadly similar amounts. Each covers half of the expense.
• In proportion to income when there is a gap. The higher-earning parent takes on a larger share, for example 60/40, so the financial effort stays balanced relative to what each can afford.

Good practice is to set this ratio once and apply it consistently. The tricky part comes when the ratio changes over time and nobody remembers which value applied to a past expense. To avoid that, the ratio should be locked in at the moment the expense is incurred: a purchase made in March stays calculated with the March ratio, even if it changes later.

Child maintenance can still apply

Many parents assume that shared custody puts an end to child maintenance. It is not automatic. When the two households have noticeably different incomes, maintenance can remain in place so the child enjoys a comparable standard of living with each parent.

In the UK, the principle used by the Child Maintenance Service is that the number of nights the child stays overnight with the paying parent affects the calculation: the more overnight stays, the more the maintenance amount is reduced. The exact figures depend on each family's circumstances, so this guide sticks to the principle without quoting rates or amounts. Whatever the arrangement, any maintenance payment comes on top of the sharing of expenses, not instead of it. It is also worth knowing that child benefit can only be paid to one parent for a given child, even in a 50/50 arrangement; the details and current rules are set out on gov.uk.

A joint account for the children

To pool shared expenses, many separated parents open a joint account dedicated to the children's costs. Each parent pays in an agreed amount, and common expenses are settled directly from that account.

A joint account has real advantages, but also limits you should be aware of.

• Advantages: shared expenses are paid from a common source, which reduces personal outlays and gives both parents visibility over the child's spending.
• Limits: it does not replace tracking. You still need to check that both parents pay in fairly, keep the receipts, and make sure the payments going out really match the shared expenses you agreed.

In other words, a joint account makes paying easier, but it is no substitute for rigorous record-keeping. Without a clear trail, you quickly slide back into mental arithmetic and rough guesses.

Keeping the accounts fair and argument-free

Whether you use a joint account or simply reimburse each other, the same rule applies: clarity prevents conflict. Three habits are enough to keep the split healthy.

• Record everything: every shared expense, with its receipt, its date and the parent who paid upfront.
• Calculate the shares: apply the split ratio to each expense, rather than redoing the sums from memory.
• Settle up regularly: balance the accounts at a steady rhythm instead of letting months of expenses pile up.

That is exactly what Kidivi is built for. The app separates ordinary expenses from extraordinary ones, applies a configurable split ratio (50/50, 60/40 and so on) that stays locked at the moment of each expense, and shows a real-time balance in both directions: you can see at a glance who owes what to whom. The detail can be viewed by month, by child and by category, and every receipt is captured in seconds with a quick scan. Once the balance is known, settling up takes a single tap, by bank transfer via QR code or through PayPal, and the locked history keeps a reliable record of everything that was shared.

In short, shared custody does not spare you from organising the children's money: it layers day-to-day costs covered by each parent on top of shared expenses divided by an agreed ratio, with child maintenance added where needed. By setting the rules early and tracking every expense methodically, you turn a potentially explosive subject into a simple shared routine.