Both witness and certify documents, but their legal authority is different. Here is how to know which one your document actually requires.
Commissioner of Oaths: for documents used within Canada
A Commissioner for Taking Affidavits witnesses signatures and administers oaths or solemn declarations for domestic use — family law affidavits, statutory declarations, vehicle ownership transfers (Form 1157), and insurance claim declarations are common examples.
Notary Public: broader authority, including international use
A Notary Public has everything a Commissioner of Oaths has, plus the authority to certify true copies of original documents and prepare documents intended for use outside Canada — passports, diplomas, powers of attorney, consent-to-travel letters for minors, and documents for foreign visa or immigration applications.
When in doubt, ask before you show up
If your document is going to another country, or needs a certified true copy rather than just a witnessed signature, you need a Notary Public. For most Ontario domestic matters, a Commissioner of Oaths is sufficient and faster. We offer both services at our Etobicoke office — walk-ins welcome, same-day service available.