It's 2 years from when the debt went into default or the creditor "OUGHT to have known" that it was defaulted on. Practically, that could be anywhere from 1 to 90 days afer the original invoice was due. As well, the creditor would need to send it out in a timely manner, not 7 months late.
They have 2 years to file a claim from that date. In Canada, unlike in some US States, creditors can still file a claim after that date with the onus being on the defendant to present the limitation period for action as a defence against the plaintiff's claim.
Read Sections 4, 5 [Discovery periods], of the link below if you want the exact wording
http://www.e-laws.gov.on.ca/html/statutes/english/elaws_statutes_02l24_e.htm
In Ontario, the courts (are supposed to anyway) use a reverse onus stance. The creditor must show the claim was filed within 2 years of the default. The judge should examine the supporting documentation of the claim and dismiss it if the filing date exceeds 2 years from the default date.
But a defendant would be wise (with outfits like Natale Law Offices around) to make sure they file a defence and show up for any pretrial settlement hearing or actual trial so as to not risk having to file a motion to set aside a default judgment from potential courtroom laxity on the part of the presiding justice. It does happen.
But I wouldn't worry for 5 seconds about any of that in a case like this.
Even if it went to trial (which it won't), just tell the judge you don't have any money, and ask the judge or 10 bucks a month. 20, if you're feeling generous. And it's not going on your credit report unless he hires a collection agency to go after it. But they won't even listen to him unless he's established a regular account with one. Very unlikely.
Complaining to the appropriate professional governing body, whether he's a CMA, CGA or CA is a waste of time. They don't like to involve themselves with petty disputes over minor invoiced fees. They're more interested in violations of their professional association standards.
In short, if you want to pay the bill and can, do so, otherwise forget about it or put it on the back burner.