Legal Question in Family Law in Utah

First, you should be aware there is no provision in the law for an automatic adjustment of child support. The code has provisions relating to how often it can be reviewed and modified but it's not automatic and any review or modification needs to be initiated by one of the parties. The parties can agree on a child support which is in excess of the guideline amount but rarely will the court adopt or allow the parties to agree to a child support amount which is less than the guidelines. Also, child support is always subject to modification.

With respect to the physical custody arrangement, I'm unclear as to what your decree provides. If the Divorce Decree awarded joint physical custody giving you 140+ per year and you agreed to set child support based on the sole physical custody guidelines, there's not much you can do. However, if the Decree awarded your ex sole physical custody and since that time, your son has started to live with you for the 140+ overnights, then you would have a basis to petition the court to modify not only child support, but child custody as well.