Like many other states, Arizona has a set of Child Support Guidelines which Arizona courts will use to calculate how much child support one parent will pay to the other. Although the amount called for under the guidelines will almost always apply to the parent without custody, in certain case, a parent with custody may also wind up paying child support.
The Guidelines, which most recently underwent a substantial revision in 2015, follows what is called the "income shares" model of calculating support. The idea is that based on each parent's income and certain expenses, the formula the Guidelines uses can approximate how much the parents would spend on the child in question if they all lived under the same roof. The support obligation is then divided based on how much each parent makes.
Arizona courts start with what is called a "presumption" that the child support called for in the Guidelines is a fair and reasonable amount and should be used. However, courts are allowed to deviate from the Guidelines if it decides that applying the Guidelines would mean an "unjust" or "inappropriate" amount of support. The court has to follow several procedures before being able to deviate, and, most importantly, it must show how the change serves the best interests of the child in question.
Even when there is no reason to deviate from them, however, Tempe residents should not conclude that calculating child support is automatic and beyond contention. Arizona's formula for figuring support is established; however, the numbers that go in to the formula, especially a parent's income, are subject to argument and are often hotly debated in family law cases.