When both parties agree on child support, they can easily establish it through a consent order, and the agreed-upon amount is deemed fair and reasonable. If disagreements persist, a hearing becomes necessary. The requesting party must present evidence to demonstrate the child's needs and fair expenses, usually using a worksheet with a presumptive correct amount. The opposing party then has a chance to counter this, potentially leading to a deviation from guidelines, though such deviations are typically rare and require strong evidence. Deviations can involve either decreasing or increasing the support amount, with the party seeking an increase needing to substantiate their case. Ultimately, the court evaluates what fair and reasonable expenses for the child are before making a determination.