SchnookoLoly said:
If you are in Canada and have been filing tax returns, then you are expected to provide an Option C. The line to provide an explanation if you are not providing it is more if you are living in another country and don't have a recent Option C to provide. I was in this boat - had been living int he UK for a few years when I applied to sponsor my husband, so I wrote a note saying I had not filed taxes in x years in Canada, but I instead provided by UK tax returns and other tax information in place of not having a current Option C. But if you are in Canada, then there's no reason you can't provide an Option C.
I second SchnookoLoly. You are required to provide Option C and if you unable to do so you are required to provide an explanation why you cant. A person should submit an additional document in lieu if they are if they are not living here or haven't filed taxes.
Quoting from the document checklist and the forms
"Make sure you include with the application the original Option-C printout obtained from the Canada Revenue Agency"
http://www.cic.gc.ca/english/pdf/kits/forms/IMM5481E.pdf
"If you do not provide this printout, provide an explanation on a separate sheet of paper" http://www.cic.gc.ca/english/pdf/kits/forms/IMM5491E.pdf
@chucky44: Option C is a more detail version of the NOA
@ spinning_sponsor: Yes it doesnt say Option-C but the OP will need to call the CRA and order for "Option-C"