“Professors Rogerson and Thompson, writing in the SSAG, tie the claim to postseparation increases in income to “some rough notion of causation”. They write at para. 14.3:
Some rough notion of causation is applied to post-separation income increases for the payor, in determining whether the income increase should be reflected in increased spousal support and, if it should, by how much. It all depends on the length of the marriage, the roles adopted during the marriage, the time elapsed between the date of separation and the subsequent income increase, and the reason for the income increase (new job vs. promotion with same employer, or career continuation vs. new venture).
In the [Revised Users Guide] Professors Rogerson and Thompson make clear that “some rough notion of causation” is not to be taken as requiring a clear line of causation between the relationship and the income increase. They state:
It would be better to describe it as a “link” or “connection”, between the marriage and the increase after separation. That has certainly been the approach of most courts, especially those in B.C. and Ontario.
Professors Rogerson and Thompson add that, strictly speaking, a finding of compensatory entitlement is not a prerequisite to a spouse sharing in post-separation income increases, particularly in long-term marriages. They say:
The basis of entitlement has a significant impact upon the degree of sharing of increases, with compensatory claims more likely to result in sharing than non-compensatory claims, but not exclusively so. There can be sharing—partial, or even full—in non-compensatory cases too, especially after long marriages.
The authors add that practically speaking, cases regarding post-separation income increases are “complex … involving a mix of facts and legal factors, with a strong discretionary element to the final judgment.”
Cameron v. Cameron, 2018 ONSC 2456 (CanLII) at 66-69