The child support enforcement agency shall review an administrative child support order on the date established pursuant to section 3119.60 of the Revised Code for formally beginning the review of the order. If the agency determines that an adjustment is necessary and in the best interest of the child subject to the order, the agency shall calculate the amount the obligor shall pay in accordance with the basic child support schedule established pursuant to section 3119.021 of the Revised Code and may add or adjust payment on arrearages in accordance with section 3123.21 of the Revised Code. The agency may not grant a deviation pursuant to section 3119.23 of the Revised Code from the guidelines established pursuant to section 3119.021 of the Revised Code. If the agency can set the child support amount the obligor is to pay without granting such a deviation from the guidelines, the agency shall do the following:

(A) Give the obligor and obligee notice, by ordinary mail, of the revised amount of child support to be paid under the administrative child support order, of their right to request an administrative hearing on the revised child support amount, of the procedures and time deadlines for requesting the hearing, and that the agency will modify the administrative child support order to include the revised child support amount unless the obligor or obligee requests an administrative hearing on the revised amount no later than fourteen days after the notice under this division is issued;

(B) If neither the obligor nor obligee timely requests an administrative hearing on the revised amount of child support, modify the administrative child support order to include the revised child support amount;

(C) If the obligor or obligee timely requests an administrative hearing on the revised amount of child support, do all of the following:

(1) Schedule a hearing on the issue;

(2) Give the obligor and obligee notice of the date, time, and location of the hearing;

(3) Conduct the hearing in accordance with the rules adopted under section 3119.76 of the Revised Code;

(4) Redetermine at the hearing revised support obligations under the administrative child support order, including adding or adjusting a payment on arrearages in accordance with section 3123.21 of the Revised Code;

(5) Modify the order to include the revised amount of child support;

(6) Give notice, by ordinary mail, to the obligor and obligee of the amount of child support to be paid under the order and that the obligor and obligee may object to the modified order by initiating an action under section 2151.231 of the Revised Code in the juvenile court or other court with jurisdiction under section 2101.022 or 2301.03 of the Revised Code of the county in which the agency that issued the order is located.

Except as otherwise provided in section 3119.772 of the Revised Code, if the agency modifies an existing administrative child support order, the modification shall relate back to the first day of the month following the date certain on which the review began under section 3119.60 of the Revised Code.

If the agency cannot set the amount of child support the obligor will pay under the administrative child support order without granting a deviation pursuant to section 3119.23 of the Revised Code, the agency shall bring an action under section 2151.231 of the Revised Code in the juvenile court or other court with jurisdiction under section 2101.022 or 2301.03 of the Revised Code of the county in which the agency is located requesting that the court issue a child support order.