Guide
How to fill in a C100 form
What the C100 is, what you need before you start, and how to tell your story clearly — in plain English.
Written by Nikkie Gilbert, McKenzie Friend and IDVA · Updated October 2026
The C100 is the form you use to ask the family court to make a decision about your children when you and the other parent can't agree. It can feel daunting, but broken down into steps it's very manageable.
What is a C100 for?
You use a C100 to apply for:
- a child arrangements order — who a child lives with, and when they spend time with the other parent
- a prohibited steps order — to stop a parent doing something, such as taking a child abroad or changing their school
- a specific issue order — to decide a particular question, such as which school a child attends
Before you start: the MIAM
In most cases you must attend a Mediation Information and Assessment Meeting (MIAM) before applying. A mediator explains whether mediation could work for you. There are exemptions — including where there is evidence of domestic abuse, or where the application is urgent. If you're claiming an exemption, the form asks you to say which one applies.
Online or paper?
You can apply online through GOV.UK or use the paper form. Online is usually quicker and guides you through each question. There is a court fee; if you're on a low income or certain benefits you may be able to get Help with Fees. Check the current fee on GOV.UK.
Step by step
1. Gather your details
Your details, the other parent's details (address if you know it), each child's full name and date of birth, and any previous or current court cases involving the children.
2. Say what you're asking for
Be specific and realistic — for example, "every other weekend from Friday after school to Sunday 5pm". Courts respond best to clear, practical proposals.
3. Explain why
Keep it factual and focused on the children's welfare, not on criticising the other parent. Short, dated points work better than long paragraphs.
4. Tell the court about safety concerns
If you're worried about domestic abuse, harm to the children, or abduction, say so. On paper this is the separate C1A form; the online application asks these questions as you go. You can also ask for special measures at court.
5. Check, sign and submit
Read everything back. Make sure dates and names are correct and that you're comfortable with every statement — you're confirming it's true.
What happens next?
The court sends the application to Cafcass (in England), who carry out safeguarding checks and may speak to both parents before the first hearing — often called the FHDRA (First Hearing Dispute Resolution Appointment). You'll be told the date in writing.
How we can help
We can help you complete your C100 and supporting statement, prepare for the first hearing and sit beside you on the day. Our fixed fee for C100 help is £150. See McKenzie Friend fees.
Common questions
Do I have to go to mediation before a C100?
Usually you must attend a MIAM first, but there are exemptions — including evidence of domestic abuse and urgent cases.
How long does a C100 take to fill in?
Allow a few hours, plus time to gather details. It helps to write your key points down first.
Can someone help me fill in a C100?
Yes. A McKenzie Friend can help you complete it in your own words. You stay responsible for checking and submitting it.
Please note: we provide non-legal support only and do not give legal advice. This page is general information, not advice about your case. Court procedures and fees change; always check the latest on GOV.UK (opens in a new tab).
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