An upward modification is only retroactive to date of filing. However if you can convince the court he materially concealed his income in past then the court will no doubt be inclines to go back to that date. Many court orders require the paying party to notify court of any change of employment or income. Please check your order. If that is in there then also file a violation petition.
As we attorneys always say spend the time and money and go see a lawyer in your area.
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It is doubtful, but one would need to know in what manner did he misrepresent his income. Did he produce tax returns & W-2's & those were fraudulent? Or did he just orally state what his income was? If there is so much money at stake, you should definitely retain a lawyer to assist you with the case.
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