According to announcement of the General Department of Vietnam Customs, member states of the ASEAN Trade in Goods Agreement (ATIGA) accepted to allow the use of HS codes 2017 on proofs of origin (including physical C/O, electronic C/O, proof of self-certification of origin) issued to the end of March 31st, 2023; From April 1st, 2024, it is required to declare according to HS codes 2022.
Regarding retroactively - issued C/O failing to meet regulations (it is not marked at "Issued Retroactively" at box 13 on the C/O), the General Department of Vietnam Customs requests Customs Departments of provinces, cities to consider accepting the electronic C/O if after the inspection of the C/O’s validity and compare it with customs declaration form and the documentation of the imported shipment, there is no doubt about goods origin.
In case of physical C/O, the General Department of Vietnam Customs requests Customs Departments of provinces, cities that they have yet to reject the C/O but they shall send report to the Customs Supervision and Control Department for verification.