For certain legal procedures, usually related to immigration, residency, investment, or marriage (or a combination of these) it may be necessary to present Mexican authorities with foreign legal documents as part of application procedure—foreign birth certificates and foreign marriage certificates are the most common.
Before the Mexican authorities will receive foreign-issued legal documents for processing, it’s necessary to get these Apostilled, sometimes referred to as Notarized.
The Apostille Convention, as it’s known, is an international treaty which many (but not all) countries are signatory to. The convention sets out a procedure through which a document issued in one of the signatory countries can be certified for legal purposes in all the other signatory countries. Mexico signed up to the treaty in 1995, making it far simpler for foreigners to present their legal documents here. The US, Europe, Australia, New Zealand, Russia, India, South Africa, and Japan are among major countries also signed-up to the treaty. If your country is not a signatory, alternative certification procedures may exist, and you should contact your consulate for advice.
Note for Canadians: Canada is not signatory to the convention, and the procedures do not apply there. Canada has instead a notarization procedure for legal documents.
In practice, when you need to submit legal documents in Mexico which were not issued in Mexico—such as birth, marriage, divorce, and death certificates, diplomas, certificates of company incorporation, etc.—you need to go to a “competent authority” in the country where the document was issued, and get any certified copies Apostilled. Each country has its own procedures for doing this and you should search online for more information, e.g. “apostille of documents in [country] or [state]”.
If you show up at the application center in Mexico (most usually an Immigration or Registrar’s office) without these types of documents having been Apostilled they will turn your application away.
Another point to note: If you get married in Mexico and live abroad (or plan to live abroad with your Mexican spouse) it’s a good idea to get your Mexican marriage certificate Apostilled (Notarized) in Mexico in case you need this for official use outside of Mexico; it needs to be done in the Mexican state you were married in. The local Registrar’s office or your wedding planner will be able to advise you about how to do this.