An assessment of child maintenance remains in place for 12 months unless income has increased or decreased by at least 25%.  If your income change is 25% or more, request a revision or supersession. Lesser changes will be included in the annual recalculation.

Other changes such as an increase in the number of nights that a child stays with you above the 52, 104 or 156 night thresholds in the past year, becoming responsible for a child in a new family or a 16-19 year old child leaving full-time, non-advanced education will reduce maintenance liability.  Further details can be found here or by contacting Child Maintenance Options.