The parties agreed child maintenance in 2007 through a family based agreement for two children, who are now age 16 and 21. The 21-year-old completed their full time education in 2017. At some point, the paying parent’s income increased, and the parties are agreed that a sum may be owing as to the difference between the sums paid and the amount that would have been calculated by the Child Maintenance Service (CMS). Could the CMS be asked to calculate arrears as to the difference between the sums paid and the sum that would have been paid had a calculation been made on the basis of the increased income, and if so for what period of time? If not, what other remedies may be available if the matter cannot be agreed?