A family-based arrangement is when parents agree child maintenance between themselves. This is the quickest and most cost effective way to sort out payments. It is also flexible and can be changed if circumstances change. The Child Maintenance Service provides information to help you work out what the payments should be and they also have an online calculator.
You both agree how much the payments should be and when they should be made. There’s no official paperwork but you can write down your agreement in case of future disagreement. However, this will not be legally binding, so if there are problems in the future, you will need to apply to the Child Maintenance Service to make a legally binding arrangement.