(a) When the court is requested to modify a child support order issued prior to July 1, 1992, for the purpose of conforming to the statewide child support guideline, and it is not using its discretionary authority to depart from the guideline pursuant to paragraph (3), (4), or (5) of subdivision (b) of Section 4057, and the amount of child support to be ordered is the amount provided under the guideline formula in subdivision (a) of Section 4055, the court may, in its discretion, order a two-step phase-in of the formula amount of support to provide the obligor with time for transition to the full formula amount if all of the following are true:

1. (1) The period of the phase-in is carefully limited to the time necessary for the obligor to rearrange the obligor’s financial obligations in order to meet the full formula amount of support.
2. (2) The obligor is immediately being ordered to pay not less than 30 percent of the amount of the child support increase, in addition to the amount of child support required under the prior order.
3. (3) The obligor has not unreasonably increased their financial obligations following notice of the motion for modification of support, has no arrearages owing, and has a history of good faith compliance with prior support orders.

(b) When the court grants a request for a phase-in pursuant to this section, the court shall state the following in writing:

1. (1) The specific reasons why (A) the immediate imposition of the full formula amount of support would place an extraordinary hardship on the obligor, and (B) this extraordinary hardship on the obligor would outweigh the hardship caused the supported children by the temporary phase-in of the full formula amount of support.
2. (2) The full guideline amount of support, the date and amount of each phase-in, and the date that the obligor must commence paying the full formula amount of support, which shall not be later than one year after the filing of the motion for modification of support.