To expound further on the above:
Child support is to be paid based upon the current income of the payor. It is for this reason that a loss of employment should result in a substantial decrease in child support - nothing in, nothing out.
To expand further... To change often requires a motion (Form 15) to have adjusted if the parties are unable to agree. There isn't an automatic systemic approach. In the absence of there being a proper agency that receives both parent's payroll notice for each payroll and then adjusts it in near-real-time you will have to deal with (in most cases) yearly adjustments on a go-forward basis.
People often choose to use the tax documents from the previous year since they are a clear indication of what last year's income was. Should this year's income differ, that will be accounted for in the next year, and so on moving forwards.
The key differentiating factor that I would add to the excellent advice given is that it should start off reading "Reasonable people often choose to use..."
At law, the "most accurate" way to assess child support would be a monthly determination of income followed by the corresponding child support payment. However, as this would lead to uncertainty for all parties and require an unreasonable amount of work to determine the monthly amount, this is not ever done in (sensible) practice.
Further to this point, if the courts want to administer justice "at law" then the system of government has to provide the service to do such. FRO can't do this. So, the justice has their hands tied when enforcing "at law". The counter argument is that there is no system in place that could support the definition "at law". Jurisprudence speaks to the go-forward basis of calculating child support.
Unfortunately, for unreasonable people this fact often doesn't sink in. Even after a qualified lawyer explains this to them. They go right back into the court room to demonstrate their "highly conflicted" pattern of dispute resolution through the courts.
If there are issues with the T4 or NOA that are not of substantial impact, one way to address the issues is to go through the income tax return when it is received the following year, calculate what child support ought to have been the previous year and see a payment flow from one party to the other if there was an overpayment or underpayment.
Again, a threshold should really be applied for "reasonableness" of this kind of pattern. If we are talking a small % difference, it is often better to just move on and not create conflict as it all washes out in the long run of calculating child support.
It all boils down to "penny wise pound foolish".
@ 250-500 an hour for a lawyer you could be looking at 8 hours of effort to recover money that may not even match the cost (2,250 - 4,520). Likely that a cost award being made is low. Especially if the costs and amount being sought are close (or the costs are higher than the amount). Doing something like this would just be evidence to the justice that you are highly conflicted and seeking nothing but more conflict rather than thinking logically about the situation.
All litigants need to realize "how" they litigate a matter is often evidence to the conflict in a matrimonial dispute and the justices take note of this. They may not talk to it but, it does impact the balance of probabilities and who is the "reasonable" party in the matter is.
Is it reasonable to litigate for a small % difference because someone got a better than expected bonus the previous year? Nope. Just take the calculation and move forward as the child support increases.
Not sure how litigating a minimal adjustment to child support demonstrates the moving party is really considering the "best interests" of the children involved. Conflict is know to be the worst thing for children. Court is from the onset a adversarial (conflicted) situation. Why start the conflict and not settle. A reasonable compromise always is in the children's "best interests".
As always, OrleansLawyer serves to impress.
Good Luck!
Tayken