When parents separate an obligation to pay child maintenance arises. If the amount is not agreed by the parents themselves, it will be assessed by the Child Maintenance Service (formerly the Child Support Agency) who apply a formula. This is now based upon the gross weekly income of the payer and is obtained from HMRC for the latest available tax year. This means that they may not be assessing your current pay rate, whether that is more or less pay than you earn now.
If your current income differs from historic income by at least 25% then the parent with care can apply for an assessment based on current income. In many cases, the parent with care will not have sufficient information concerning the other parent’s income to know when something is incorrect and indeed in most cases there will be insufficient knowledge of the system to know that something can be done to rectify it. In the absence of this information, the annual review will be relied upon when the payer’s income is reconsidered based on updated income data provided by HMRC.
The system means that there are many cases which the payment is more or less then it should be based on the payers existing financial circumstances. It is far preferable for the parents to reach agreement rather than leaving the figures to be calculated by the Child Maintenance Service.