It collected the data from 268 e-commerce platforms, and the vendors had carried out transactions worth VND4.5 trillion ($190.8 million) by the end of last year, it said.
The value could be even higher and it is working to improve its data collection by using artificial intelligence, it added.
But it has yet to collect information from major Vietnamese e-commerce platform Tiki.
Starting in November last year e-commerce platforms are required to provide tax authorities with detailed information about their vendors.