Child maintenance payments have been calculated based on information from HMRC. I know my ex will not agree with payments and will do anything to pay less. I know the 25% rule but if he appeals what sort of proof will cms ask him? Just a payslip? If that's the case he will easily manipulate everything once again as all he has to do is work less hours and not work overtime and once they reduce payments he will go back to work his "normal hours". If this was the case surely cms would find out when they do the annual review next year and get the gross income from HMRC?