Your co-parent won't pay their share of the children's expenses: what to do

You keep covering the children's costs, school lunches, a pair of glasses, the football club registration, and the other parent never pays their share. It is one of the most common frustrations between separated parents, and it drains you as much as it irritates you. The good news: there is a calm, step-by-step way to handle it. The aim is not to inflame the relationship, but to get your side in order, keep a clean record, and leave a door open to agreement at every stage.

1. Establish the facts and stay calm

Before anything else, take a breath. A late or missing repayment does not always mean bad faith: it can be forgetfulness, a disagreement over the amount, a temporary money problem, or a genuine misunderstanding about which costs are supposed to be shared. Starting from the assumption that things can be settled amicably saves you time and energy.

What matters is separating what you can control from what you cannot. You do not control the other parent's reaction. You do control the clarity of your request and the quality of your evidence. That is precisely where the next steps are won or lost. A factual, measured tone, with no personal reproach, defuses a good part of the tension on its own.

Keep one distinction firmly in mind, because in the UK it decides which route you will follow later. Child maintenance is the regular payment for everyday costs, worked out through the Child Maintenance Service, a family-based arrangement or a court order. Shared extra expenses, one-off and significant costs such as orthodontics, a residential school trip or an expensive activity, sit outside that payment and rest on whatever agreement or order covers them. Knowing exactly which category a cost falls into, as set out in our list of extraordinary expenses, clarifies the debate immediately.

2. Gather your evidence: the foundation of everything

No step you take, friendly reminder, formal letter, mediation or court, will hold up without evidence. It is the base of the whole ladder. Before you even write to the other parent, put your paperwork in order. Concretely, that means collecting:

• the dated proof of each expense (invoices, tickets, receipts, confirmations);
• a clear history showing who paid what, when, and for which child;
• a record of the repayments already made, so the outstanding balance cannot be disputed;
• the nature of each cost (maintenance territory or shared extra expense) and the share you expect from the other parent.

The thread running through everything that follows fits in one sentence: solid, dated, neutral documentation changes everything. A vague account is easy to contest; a precise account, backed by dated documents, leaves far less room for argument.

A tool for documenting calmly

Keeping this record by hand, in a spreadsheet or in an inbox, works up to a point but stays fragile: a receipt goes missing, a line gets forgotten, you can no longer tell whether an amount was repaid. That is exactly the problem Kidivi was built to solve. Its solo mode lets you document every expense from your side, even if the other parent never opens the app, which matters most when you are documenting expenses with an uncooperative co-parent. The history is locked: a correction creates a new version, nothing disappears, which makes the record hard to challenge.

To strengthen the value of your documents, a SHA-256 fingerprint of each receipt is calculated before any compression, a kind of digital seal showing the file has not been altered after the fact. Everything can be brought together in a chronological, verifiable PDF export, designed to be presented clearly if the matter ever takes a more formal turn. You also see the balance in real time, with the split between everyday costs and extra expenses applied according to a formula fixed in advance.

The point is not to turn every expense into a war file. It is to be able, on the day you need it, to produce a clean account in a few seconds rather than digging through months of emails.

3. The friendly written reminder

Once your evidence is in order, the first move is almost always the simplest: a written reminder. A text or an email has two advantages: it leaves a dated trace, and it opens the conversation without dramatising anything.

A few principles make this reminder effective:

• Stay factual. Set out the account, the amounts, the dates and the share you expect. Avoid personal reproaches.
• Stay courteous. A neutral, respectful tone invites a constructive answer far more readily.
• Be precise. Attach or reference the receipts concerned, and state clearly what you are asking for.
• Keep a copy. Save the email or the message thread; that trace may count later.

Very often, a clear reminder with no edge to it is enough to unblock the situation, especially when the delay came from simple forgetfulness or confusion over the figures.

4. The formal letter

If the friendly reminder goes nowhere despite one or two follow-ups, the next step is usually a more formal written demand, often called a letter before action. It sets out the account, the share due, and invites the other parent to settle. In practice it is often sent by recorded delivery, so that you keep proof of posting and receipt.

This letter marks a change of register: you move from an informal nudge to a written, dated demand that is clearly identified as such. It is not a court procedure in itself, but it sometimes lays the first stone of one, and it shows you gave the other parent a fair chance to put things right.

This article stays general and informative, and it does not replace professional advice. The exact form, content and timing of a formal letter depend on your situation and on the rules that apply where you live: take advice from someone qualified before committing to a formal step.

5. Family mediation

Before contemplating a confrontation in court, family mediation offers a calmer path. It brings both parents together, with the help of a neutral, trained third party, to try to reach an agreement on the sticking points, here the sharing and repayment of the children's costs.

Its advantages are concrete: it generally costs less and moves faster than proceedings; it preserves the relationship better, which matters when you still have to raise a child together; and it produces solutions both parents helped build, which tend to be respected for longer. Here again, arriving at mediation with a clear, documented account helps refocus the discussion on facts rather than grievances.

Mediation is well established in the UK, with dedicated services and accredited professionals, and it is usually worth exploring before any escalation towards court.

6. When it has to go further: the CMS and the courts

When everything else has failed, the route depends on which kind of money is at stake, which is why the distinction from the beginning of this article matters so much.

For unpaid child maintenance, the UK has a public mechanism. If your maintenance is arranged through the Child Maintenance Service, or you move it there, its Collect and Pay service can collect the payments and pass them on. If payments are still missed, the CMS has enforcement powers, from taking money directly from earnings or benefits to court-based action. The details and conditions are on gov.uk, and we cover the steps in our guide to child maintenance that is not being paid.

For disputed extra expenses, the CMS is not the right door: these costs sit outside the maintenance calculation. The route is agreement between the parents, then mediation, then the family court, which can rule on the dispute and, where appropriate, give you an enforceable decision. What weighs in that setting is a clear file, as explained in our article on proving children's expenses in court.

Whichever door you knock on, the same observation comes back: a clear, chronological, verifiable file saves you precious time. That is also the spirit of the solicitor-ready PDF export offered by Kidivi: presenting, when it counts, a dated and coherent history rather than a heap of loose documents.

What to remember

Faced with a co-parent who does not pay their share, the progression is almost always the same: stay calm, document, remind amicably, formalise if needed, try mediation, then consider the CMS route for maintenance or the family court for shared extra expenses. Every step leaves a chance for agreement, and every step rests on the same foundation, dated and neutral evidence.

That is where documenting as you go, rather than in a panic on the day of the conflict, makes all the difference. Kidivi lets you start on your own, in solo mode, without waiting for the other parent. Your data stays in the European Union, there is no advertising, and the app works offline, so the record builds itself quietly in the background until the day you need it.