When to submit the health certificate to the commodity inspection bureau is a good time to export abroad, must it be after sailing? What about the certificate of origin?

Aren't you going to do commodity inspection, too? When you do this, just hand in the relevant information of the health certificate on the way.

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You can start making the certificate of origin after shipment, as long as you estimate the time when it will be signed, and don't delay sending/submitting the documents.

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Your last question is "... that is, can you apply for a health certificate before loading when the loading quantity is determined?" "

You're right, that's what we said above.