(1) In lieu of legal proceedings instituted to obtain a modification for an order for support, a written stipulated agreement for modification executed by the responsible parent when acknowledged before a clerk of the court having jurisdiction over those matters or a notary public and filed with and approved by the judge of that court shall have the same force and effect, retroactively and prospectively, in accordance with the terms of the agreement as an order for modification of support entered by the court, and shall be enforceable and subject to later modification in the same manner as is provided by law for orders of the court in those cases.

(2) With respect to a child support order in cases initiated or enforced by the Department of Human Services under Title IV-D of the Social Security Act, in which the department has determined that a modification is appropriate, the department shall send a motion and notice of intent to modify the order, together with the proposed modification of the order under this section to the last known mailing address of the defendant. The notice shall specify the date and time certain of the hearing and shall be sent by certified mail, restricted delivery, return receipt requested; notice shall be deemed complete as of the date of delivery as evidenced by the return receipt. The required notice may also be delivered by personal service in accordance with Rule 4 of the Mississippi Rules of Civil Procedure insofar as it may be applied to service of an administrative order or notice. The defendant may accept the proposed modification by signing and returning it to the department before the date of hearing for presentation to the court for approval. If the defendant does not sign and return the proposed modification, the court shall on the date and time previously set for hearing review the proposal and make a determination as to whether it should be approved, in whole or in part.

(3) Every three (3) years, the Department of Human Services shall notify both parents of their right to request a review, and upon the request of either parent, or if there is an assignment under Section 43-19-35, the department, after a review and determination of appropriateness, or either parent may seek an adjustment to a support order being enforced under Section 43-19-31 in accordance with the guidelines established under Section 43-19-101, if the amount of the child support award under the order differs from the amount that would be awarded in accordance with the guidelines, taking into account the best interests of the child involved. If a recipient of Title IV-D services receives TANF, the Department of Human Services shall conduct a review every three (3) years and, after a determination of appropriateness, shall seek an adjustment to a support order according to the guidelines under Section 43-19-101. No proof of a material change in circumstances is necessary in the three-year review for adjustment under this subsection (3). A preexisting arrearage in support payments shall not serve as a bar to the department’s review and adjustment procedure. Proof of a material change in circumstances is necessary for modification outside the three-year cycle.

(4) Any order for the support of minor children, whether entered through the judicial system or through an expedited process, shall not be subject to a downward retroactive modification. An upward retroactive modification may be ordered back to the date of the event justifying the upward modification.

(5) If a downward modification is determined to be warranted under the guidelines contained in subsection (3), the noncustodial parent’s arrearage, if any, shall not be a basis for contesting the downward modification in any later legal proceedings.