In divorce cases, fraud is relatively rare but personal motives can lead to a party, for reason of wanting to keep their perceived "fair" share, minimizing asset values and incomes, or possibly even omitting them altogether, to retain or obtain a greater share of the marital pot.
In family law, financial disclosure disputes are governed by Rule 12.285. Under this procedural rule, comprehensive disclosures are required in any case that involves a dispute over money. All assets and incomes must be identified when obtaining a fair settlement while going through a divorce. If one side is refusing to provide explanations or hand over statements or any other financial documentation or there is a lot of information absent when you receive the papers. Maybe the figures are just not stacking up and there is no way their current lifestyle could be afforded based on declared incomes and known assets.