What this tool does

This tool helps you challenge a Child Maintenance Service decision you think is wrong. It explains the mandatory reconsideration you have to ask for before any appeal, the rules that apply to your particular dispute, the evidence that is most likely to change the outcome and what happens if the CMS does not change its mind.

It gives general guidance, not legal advice, and it cannot tell you what the CMS will decide.

When to use it

The most common reason people use it is shared care: you look after your child for a good part of the week but the CMS is not counting those nights, or the other parent has told the CMS they are the main carer when they are not. It also covers calculations based on the wrong income, arrears you dispute, and payments that should have stopped or carried on when a child turned 16 and left or stayed in education.

Grandparents and other family members often ask on a parent's behalf. The tool explains what the parent needs to do themselves and how you can help them gather evidence.

How it works

You tell us whether you pay or receive, what you think is wrong, roughly how many nights the child spends with the paying parent, when the decision was made and what evidence you have. The tool explains your time limits, the shared care bands, the rules on older children and the steps to take in order. Nothing you enter is saved, and you do not need to give your name or email to use it.

Time limits matter, so act quickly. If your case is complicated or there is a lot of money involved, free help from Citizens Advice or a family law solicitor is worth getting.