This web site is primarily concerned with the second, major type of problem. Many of these are not simply problems with the child support legislation and with the CSA. They are problems with the whole "system" of the way that the children of separated parents are brought up. (For example, one of the most important recent improvements to child support in the UK is the disregard of child support in the tax credit system. This was actually nothing really to do with child support legislation or the CSA, but it made many lone parents and their children better off and improved the relationships among many separated parents and their children).
This web site also identifies several of the first, lesser, type of problem. This is easy to do because there are a lot of them! They are separated out when discussing "What next?"
The way that the current scheme uses the income of the new partner of the NRP is a continuing source of resentment and friction. It was actually part of a well-meaning attempt to allow the NRP's housing costs to be taken into account, but comes into the category "the road to hell ..."!
The reformed scheme takes into account the NRP's step children. The NRP pays less for children s/he is responsible for as a result of children s/he is not responsible for. It isn't wrong per se to take "social parenting" into account, but it is wrong to do so outside of a considered strategy on social parenting.
This may feel the right thing to do, but it is impossible to have a fair and workable way of doing so using a child support system.
Other mechanisms are needed.
In spite of the Income Support disregard being considered "good", it could be significantly better. It still reveals the hand of the Treasury trying to minimise social security payments to lone parent households, some of the most poverty-struck households around. This must change in future.
Here is just one symptom of its failings. Suppose the parents share care by an identical amount. The amount paid by the person who doesn't claim Child Benefit (aka "the father") to the person who claims Child Benefit (aka "the mother") varies according to the number of children. Suppose that he earns £210 per week net: