Certificate of origin, declaration of origin, or USMCA certification
All three say where goods came from. They are not interchangeable, and sending the wrong one either costs your buyer a duty rate or gets the shipment held while the right one is obtained.
Certificate of origin
The general-purpose one. It states origin for a shipment and is typically certified by a chamber of commerce, which checks your documents against each other and stamps the signature. It is non-preferential: it proves where the goods are from, but claims no reduced duty.
You need one when the destination requires it, when a letter of credit lists it, or when quota, labelling or embargo rules turn on origin. Several Middle Eastern markets additionally require consular legalisation on top of the chamber stamp, which is a separate step with its own lead time.
Declaration of origin
The same statement, made by you, without a chamber. A self-certified declaration, usually on letterhead and signed.
It works where the buyer or the destination accepts self-certification, and it is faster and cheaper because nobody else has to touch it. It fails where the destination specifically requires certification by a competent authority. If your buyer says "we just need something saying it's made in Vietnam", this is that.
The thing to be clear about: self-certified does not mean informally asserted. You are still standing behind it, and a wrong declaration is a wrong declaration regardless of who stamped it.
USMCA certification of origin
A different instrument entirely. This is a preferential claim: it says the goods qualify under the US–Mexico–Canada agreement and therefore attract a reduced or zero rate.
Three things surprise people migrating from NAFTA:
There is no official form. The certification is nine required data elements plus a certification statement, and they may appear on any document — including the commercial invoice itself.
The importer, exporter or producer may certify, and the document must state which. Under NAFTA only the exporter could.
It can be a blanket covering identical goods for up to twelve months, rather than one certification per shipment.
Records supporting it must be kept for five years, and a verification can ask for bills of materials and production records, not just the certificate.
Which one, in practice
Ask what the document is for.
If someone needs to know where the goods are from, and the destination accepts your word, that is a declaration of origin.
If someone needs it verified by a third party, or the destination or a letter of credit requires it, that is a certificate of origin.
If the point is a lower duty rate under a trade agreement, none of the above will do. You need that agreement's own instrument — a USMCA certification for North America, an EUR.1 movement certificate or origin declaration for EU preferential trade, a Form A under GSP schemes. A general certificate presented for a preference claim gets the claim refused, and the duty saving is usually why anyone was asking.
The failure that costs most
Claiming preference on a general certificate, or certifying preferential origin without having applied the rule of origin for that tariff heading. Preferential origin is not "made in", it is a technical test — usually a change of HS classification or a percentage of local value — applied per heading. Getting it wrong is not a paperwork slip; it is claiming relief you were not entitled to, and it is recoverable from the importer with interest years later.