Florida Statute § 61.14(1) governs “[e]nforcement and modification of support, maintenance, or alimony agreements or orders.” That section provides in relevant part:

[W]hen a party is required by court order to make any [support, maintenance, or alimony] payments, and the circumstances of or the financial ability of either spouse changes … either party … may apply … for an order decreasing or increasing the amount of support maintenance, or alimony, and the court has the jurisdiction to make orders as equity requires, with due regard to the changed circumstances or the financial ability of the parties or the child, decreasing, increasing, or confirming the amount of separate support, maintenance, or alimony provided for in the … order.

Under Florida law, a fundamental requirement for seeking to modify child support payments is a showing of a substantial change in circumstances. Overby v. Overby, 698 So. 2d 811, 813 (Fla. 1997), citing Chastain v. Chastain, 73 So. 2d 66 (Fla. 1954), Deatherage v. Deatherage, 395 So. 2d 1169 (Fla. 5th DCA 1981).

Florida Statutes § 61.13 governs the power of courts to issue orders regarding child support. Overby, 698 So. 2d at 813. That section provides in relevant part:

(1)(a) … The court initially entering an order requiring one or both parents to make child support payments shall have continuing jurisdiction after the entry of the initial order to modify the amount and terms and conditions of the child support payments when the modification is found necessary by the court in the best interests of the child, when the child reaches majority, or when there is a substantial change in circumstances of the parties.

Under section 61.13(1)(a), a court that initially entered an order requiring a parent to pay child support has continuing jurisdiction to modify the amount of the support under three circumstances: (1) modification is in the best interests of the child; (2) modification is necessary because the child has reached majority; and (3) when there has been a substantial change in circumstances. Overby, 698 So. 2d at 813. The party seeking the modification in child support carries the burden of establishing that modification is necessary. Id. at 813-14, citing Deatherage, 395 So. 2d 1169. Further, when the child support payments were established based on an agreement by the parties that was subsequently incorporated into an order, the party seeking modification carries an even heavier burden. Overby at 814, citing Tietig v. Boggs, 602 So. 2d 1250 (Fla. 1992).