What is the retroactive nature of a claim for spousal support?

I have already made an award of retroactive child support. However, as confirmed in Kerr v. Baranow, 2011 SCC 10 (CanLII), [2011] 1 S.C.R. 269, different considerations apply concerning spousal support. There is a presumptive entitlement to child support that is described as “automatic”; therefore, the issues of notice and lack of diligence are less important in considering retroactivity. At para. 208, the distinction is made clear as follows: In contrast, there is no presumptive entitlement to spousal support and, unlike child support, the spouse is in general not under any legal obligation to look out for the separated spouse’s legal interests. Thus concerns about notice, delay and misconduct generally carry more weight in relation to claims for spousal support.