In any action or proceeding in which the court determines the amount of child support that will be ordered to be paid pursuant to a child support order or at any time a child support enforcement agency determines the amount of child support that will be paid pursuant to an administrative child support order, the amount of child support that would be payable under a child support order, as calculated pursuant to the basic child support schedule and applicable worksheet through the line establishing the actual annual obligation, is rebuttably presumed to be the correct amount of child support due.