What is the test for retroactive orders for special expenses and special expenses?

The respondent cites Semancik v. Saunders, 2011 BCCA 264, in addressing the question of special expenses and retroactive orders concerning those amounts, reiterating the principles from D.B.S. v. S.R.G., 2006 SCC 37 at para. 98. These principles include: a) a parent’s obligation to support a child must be commensurate with that parent’s income; b) the child’s right to support exists independent of any statute or court order. Both parents are responsible to ensure that the payor fulfils his obligations; c) the court is required to make an award that recognizes the failure of a payor parent as it enforces the obligation that should have been fulfilled; d) Retroactive awards may not be appropriate where there is no discernible benefit to the child or may cause hardship to the parent.