They were one of the major contributors to personal income tax collection in the first five months, which rose by nearly 13 percent, Cao Anh Tuan, head of the General Department of Taxation, said.
Vietnam imposes a flat 0.1 percent capital tax on every stock sale.
Other contributors were real estate (up 183 percent) and personal investment (up 169 percent), Tuan added.
In May, an average of 3,600 individual stock trading accounts were opened each day, the highest ever. The number of accounts now has risen 11-fold since January 2020 to 3.2 million, or one each for 3.26 percent of the population.
In the first five months of this year, 480,000 accounts were opened.
In the period, the benchmark VN-Index gained over 20 percent, the highest in Asia.