Every party to a support order has an affirmative duty to notify the court upon there being a change in income. If you were to file a support complaint/petition with the court, ordinarily, the the obligor's support obligation becomes effective the date of the filing of the petition. Having said that, the law allows the court to modify a support obligation retroactive to the date of the actual change in income, even if this date preceeds the filing of the petition, in the event that you are able to prove that the obligor wilfully failed to notify the court of the change in his/her income. In other words: you have an argument to recoup support owed to you that you did not receive but-for your ex's failure to disclose this additional income, but you should certainly contact an attorney in your area to discuss your options in this regard.
You can certainly request a support modification based on this. The chances of success will be based on whether or not you can show that he had the position before he admitted to having it. That withholding of information could be fraudulent and therefore it could void the most recent agreement
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