proof from your child or grandchild that he or she meets the low income cut-off (LICO), and
http://www.cic.gc.ca/english/information/applications/guides/5256ETOC.asp#incometables
http://www.cic.gc.ca/english/pdf/kits/forms/IMM5484E.pdf
Your income, not theirs.
You can provide copy of, T4, NOA, or Option A.
Basically, You have to prove you make enough to support them financially.
It doesn't specifically say what document is required to prove this.
Good news is that, it's not as strict as sponsoring them for immigration, where you MUST prove with your tax reports that you make more than LICO for past 3 years.
Back when I applied, I just started new job and didn't have T4 or NOA from previous year, that's more than LICO requirement.
But I sent them all my pay stub from new job to show that with new job and higher pay, I am making more than LICO.
You can explain all that in the invitation letter.
Dont' quote me on this, when I applied 4 years ago, they just launched Super Visa maybe they were more flexible and less by the book.
