“To summarize, where the payor applies under s. 17 of the Divorce Act to retroactively decrease child support, the following analysis applies:
(1)The payor must meet the threshold of establishing a past material change in circumstances. The onus is on the payor to show a material decrease in income that has some degree of continuity, and that is real and not one of choice.
(2) Once a material change in circumstances is established, a presumption arises in favour of retroactively decreasing child support to the date the payor gave the recipient effective notice, up to three years before formal notice of the application to vary. In the decrease context, effective notice requires clear communication of the change in circumstances accompanied by the disclosure of any available documentation necessary to substantiate the change and allow the recipient parent to meaningfully assess the situation.
(3) Where no effective notice is given by the payor parent, child support should generally be varied back to the date of formal notice, or a later date where the payor has delayed making complete disclosure in the course of the proceedings.
(4) The court retains discretion to depart from the presumptive date of retroactivity where the result would otherwise be unfair. The D.B.S. factors (adapted to the decrease context) guide this exercise of discretion. Those factors are: (i) whether the payor had an understandable reason for the delay in seeking a decrease; (ii) the payor’s conduct; (iii) the child’s circumstances; and (iv) hardship to the payor if support is not decreased (viewed in context of hardship to the child and recipient if support is decreased). The payor’s efforts to pay what they can and to communicate and disclose income information on an ongoing basis will often be a key consideration under the factor of payor conduct.
(5) Finally, once the court has determined that support should be retroactively decreased to a particular date, the decrease must be quantified. The proper amount of support for each year since the date of retroactivity must be calculated in accordance with the Guidelines.
It is also helpful to summarize the principles which now apply to cases in which the recipient applies under s. 17 to retroactively increase child support:
a) The recipient must meet the threshold of establishing a past material change in circumstances. While the onus is on the recipient to show a material increase in income, any failure by the payor to disclose relevant financial information allows the court to impute income, strike pleadings, draw adverse inferences, and award costs. There is no need for the recipient to make multiple court applications for disclosure before a court has these powers.
b) Once a material change in circumstances is established, a presumption arises in favour of retroactively increasing child support to the date the recipient gave the payor effective notice of the request for an increase, up to three years before formal notice of the application to vary. In the increase context, because of informational asymmetry, effective notice requires only that the recipient broached the subject of an increase with the payor.
c) Where no effective notice is given by the recipient parent, child support should generally be increased back to the date of formal notice.
d) The court retains discretion to depart from the presumptive date of retroactivity where the result would otherwise be unfair. The B.S. factors continue to guide this exercise of discretion, as described in Michel. If the payor has failed to disclose a material increase in income, that failure qualifies as blameworthy conduct and the date of retroactivity will generally be the date of the increase in income.
e) Once the court has determined that support should be retroactively increased to a particular date, the increase must be quantified. The proper amount of support for each year since the date of retroactivity must be calculated in accordance with the Guidelines.”