The department will conduct its own investigations among possible tax evaders and will hand over their reports to the police if signs of law infringement are found, it said in a notice to municipal and provincial authorities.
Anyone who sells or receives commission from livestream sales is subject to taxes, it added.
An online seller with a revenue of VND100 million ($4,300) a year and a person who receives commission from livestreaming activities are subject to personal income tax of between 5% and 35%.
In the first six months the tax department examined 43,000 businesses and individuals on their tax payment.
They paid a total of VND9.98 trillion in taxes, up 53% year-on-year, as a result of the examination.
The department also found 4,560 cases of tax violations and collected VND300 billion in taxes and fines.