Patent opposition in Vietnam can be done, either before the patent is granted, by filing pre-grant opposition under Article 112 of Vietnam IP Law, or after the grant of the patent by filing a post-grant opposition which serves as a patent invalidation proceeding per Article 96 of Vietnam IP Law.

The grounds for both pre-grant and post-grant oppositions in Vietnam are the same and there is nothing which prohibits a pre-grant opponent from subsequently filing a post-grant opposition. The Pre-grant opposition can be made at any time after the patent application has been published but before the grant of a patent. Publication of patent applications in Vietnam is made in 19th month from the priority date or within 02 months from the date of acceptance as to form, whichever is later. Any natural or juridical person. Legal interest is not required. Any person may, in writing to the IP Office of Vietnam, contest the grant of a patent in Vietnam.

Grounds for patent opposition in Vietnam:

• The right to file the application.
• The priority right.
• Protection criteria in which the subject matter of the invention is not patentable (e. (i) Inventions lacking any inventive step over any prior publication or over any prior use; (ii) inventions lacking novelty (inventions that were publicly known in Vietnam or a foreign country, prior to the filing of the patent application; inventions that were publicly worked in Vietnam or a foreign country, prior to the filing of the patent application; and (iii) inventions that were described in a distributed publication, or inventions that were made publicly available through an electric telecommunication line in Vietnam or a foreign country, prior to the filing of the patent application); (iii) inventions not having an "industrial applicability")
• Other matters relating to the application (e.g. the disclosure of the invention by which it is to be performed is not sufficient and clear; the patentee has failed to disclose or has furnished false information regarding foreign applications).

The grounds for both pre-grant and post-grant oppositions in Vietnam are the same and there is nothing which prohibits a pre-grant opponent from subsequently filing a post-grant opposition (a patent invalidation) in Vietnam.