Child support calculations include all income sources. If your spouse's job has overtime payment, it will be figured into the equation used to determine the amount of support. The same is true for any type of sideline income, whether it's part-time employment, moonlighting of some sort, or a small side business in addition to a regular job. So, if your ex gets a new job in which overtime is available, and he or she begins to accumulate a significant amount of additional income, it may be possible to make a claim for upward modification of the amount of child support you receive. If you are the payor, then of course you might become subject to these obligations.