How to Apply for Child Maintenance UK (2026) — Full Step-by-Step Guide

Right, so. I applied for child maintenance on a Tuesday night after the kids were asleep, a glass of wine within arm’s reach, absolutely certain it would take twenty minutes. It took forty-five, mostly because I didn’t have my ex’s National Insurance number and spent ten minutes digging through old paperwork I hadn’t touched since the divorce. Lesson one, before we even start: gather your documents first. Don’t do what I did.

If you’re staring down this process and feeling a bit lost, here’s exactly what happens, in the order it happens, minus the bits nobody tells you.

Quick Refresher: Who This Applies To

In England, Wales, and Scotland, this goes through the Child Maintenance Service (CMS) — a government-run service that calculates and, if needed, collects payments between parents who live apart. You’ll usually go this route if you and the other parent can’t agree on a private arrangement, or a private one has broken down. If you can sort it between yourselves without government involvement, that’s genuinely the faster, cheaper route — CMS is the fallback, not the default.

How Do I Apply for Child Maintenance Online in the UK?

Here’s the actual sequence, step by step.

Step 1: Get Your Reference Number First

Before you can use the main application portal, you need a unique reference number. If you don’t already have one, you get it through the “Get Help Arranging Child Maintenance” service on GOV.UK — a short initial call or online form where they take some basic details and text or email you the reference number. Do this first; you can’t skip straight to the full application without it.

Step 2: Create Your Account

Head to the Child Maintenance Service portal on GOV.UK, choose “start now,” and set up an account with your email address. You’ll need this account to check your case status later, so use an email you actually check.

Step 3: Fill in Your Details

You’ll enter your own details — name, address, phone number, and National Insurance number — plus your child’s details (name, date of birth, and who currently gets Child Benefit for them, since that speeds things up).

Step 4: Provide Information About the Other Parent

This is the bit that trips people up, especially if contact has broken down. You’ll be asked for whatever you know: full name, date of birth or approximate age, address or last known location, phone number, and National Insurance number if you have it. If you don’t know something, say so — don’t guess, and don’t leave the application half-finished waiting until you track it down. The CMS can work with partial information and follow up themselves.

You do not need to contact your ex directly to do any of this, and if you’re worried about them finding out your address, the CMS can keep your personal location details from being shared with them.

Step 5: Submit and Wait for Contact

Once submitted, CMS may call either parent for extra details — things like the paying parent’s income, employment, or how many nights the child stays with them. This is normal. Ignoring their calls just delays things.

Documents (and Information) Required for Maintenance

People ask this expecting a big pile of paperwork. In reality, it’s less “documents” and more “information you need to have on hand.” Here’s the practical checklist I wish I’d had before I started:

• Your own National Insurance number
• Your bank details (for receiving payments, if that’s your role)
• Your child’s full name, date of birth, and whether Child Benefit is being claimed for them
• The other parent’s name, date of birth, address (or last known one), and phone number
• Their National Insurance number, if you happen to know it
• Details of any existing maintenance arrangement, if one exists
• How many nights a week (roughly) the child stays with the paying parent, since this affects the final calculation

You don’t need payslips or bank statements from the other parent — the CMS gets their income information directly from HMRC once the case is opened, which honestly was one of the more reassuring parts of the whole process. You’re not responsible for proving what they earn.

What’s the Biggest Factor in Calculating Child Support?

Hands down, it’s the paying parent’s gross weekly income. Everything else — number of children, shared care nights, other kids in their household — adjusts that base figure up or down, but income is what the whole formula starts from. CMS pulls this straight from HMRC records, which is why self-employed income (based on tax returns) can sometimes create delays or disputes compared to PAYE employment, where the figure is more straightforward.

After income, the next biggest factors are:

• Number of qualifying children the payment covers
• Shared care — how many nights per week the child stays overnight with the paying parent, since more overnights reduces the amount owed
• Other children the paying parent supports in their own household, which is deducted from their income before the main calculation

What’s the Minimum You Can Pay for Child Maintenance?

The CMS formula runs on a few income bands, and at the lower end there’s a flat rate, currently set at £7 a week, which applies to paying parents with a low gross income or those receiving certain benefits. Below that, there’s a nil rate — effectively £0 — which applies in specific circumstances, such as the paying parent being a full-time student, in prison, or under 16.

Worth flagging: these exact thresholds and the flat-rate figure are reviewed periodically by the government, so treat “£7 a week” as the current benchmark rather than a number carved in stone — always double-check the live figure on GOV.UK before relying on it for your own case, especially if you’re reading this well into 2026 or later.

One thing that surprised me: there used to be a £20 fee just to apply. That’s been scrapped — applications through the CMS are now free, which was a genuinely welcome change from when I first looked into this years ago.

Common Mistakes to Avoid

• Applying without your reference number first — you’ll just hit a wall and have to backtrack.
• Guessing at details instead of saying “I don’t know.” Wrong information causes more delays than missing information.
• Assuming maintenance is backdated. It usually isn’t — CMS collects from the date of your application onward, not from when you separated, so don’t sit on this if payments have already stopped.
• Forgetting to update shared care changes. If overnight stays shift significantly, the amount should be recalculated — it won’t happen automatically unless you report it.
• Mixing up child maintenance with contact arrangements. These are handled completely separately; sorting maintenance doesn’t affect custody or visitation rights, and vice versa.
• Not checking current thresholds before assuming a figure. Flat rates and fee rules change — always verify on GOV.UK rather than trusting an old article (including this one, eventually).

Final Thoughts

I won’t pretend this process is fun. Nobody enjoys typing their ex’s date of birth into a government form at 10pm. But once the case is set up, it genuinely does run in the background — HMRC feeds the income data, CMS does the maths, and you’re not stuck chasing anyone for payslips or having awkward money conversations every month. The hardest part is just getting the application started with accurate information, and if you’ve read this far, you’re already ahead of where I was that Tuesday night with my glass of wine and missing paperwork.

FAQ

How do I apply for child maintenance online in the UK?
Get your unique reference number through “Get Help Arranging Child Maintenance” on GOV.UK first, then create an account on the Child Maintenance Service portal and submit your details, your child’s details, and whatever information you have on the other parent.

What documents are required for child maintenance?
Mainly information rather than formal documents: your National Insurance number, bank details, your child’s details, and the other parent’s name, address, date of birth, and NI number if known. CMS gets income data directly from HMRC, so you don’t need payslips.

What’s the minimum you can pay for child maintenance?
There’s a flat rate (currently £7 a week) for low-income paying parents, and a nil rate (£0) in specific situations like full-time students or those in prison — but always check the current GOV.UK figures, as these are reviewed periodically.

What is the biggest factor in calculating child support?
The paying parent’s gross weekly income is the primary factor, adjusted by the number of children covered, shared care overnights, and any other children in their household.