Even if you think your financial situation will improve in the future, it important to essentially 'lock in the date' by filing a modification petition when your financial circumstances significantly change for the worse. In the event a period of unemployment extends beyond what was expected, modifications to the child support order are retroactive to the date the modification was filed. Failure to file a modification of child support keeps the existing order going and all payments due. Interest will be assessed on all late payments, quickly snowballing into significant arrears.