What constitutes a substantial change in circumstance?
I had a child support order entered in December and barely three months later my ex-wife is trying to modify the support order citing a "substantial change in circumstances."
I am not licensed to practice law in your jurisdiction, but I can provide you with a general answer to your divorce and child custody question.
The standard is purposely nebulous to give courts wide discretion, but generally, the term "substantial change in circumstances" requires that the facts on which the prior order was based differ from the present facts and the difference is enough to justify the court considering whether to modify the order.
A substantial change in circumstances can include a significant increase or decrease in income or expenses for either party. For instance, an individual may qualify for modification if he or she loses a job or becomes injured or infirm.
In your case, if the motion for modification only deals with support, the court will likely only review the financial circumstances between your order from December and the date your ex-wife filed her motion. Since it appears her motion was filed coextensively or shortly after your original child support hearing/order, it is unlikely that a substantial change exists.
To fully advise you on your situation, a complete understanding of your situation is necessary. I recommend contacting a family law attorney to review your case.