The decree requires banks to provide the account balance and transaction details to tax authorities upon request.
While the current law does state that the banks are required to provide authorities with information, the nature of such information was not specified.
Under the decree, banks will also need to provide monthly details on the newly opened or closed accounts of taxpayers.
The stated purpose of the decree is to allow authorities supervise and examine the tax responsibilities of citizens as e-commerce develops rapidly in Vietnam.
The decree also requires banks to pay tax dues on behalf of foreign organizations doing e-commerce and digitized business in Vietnam with local organizations and individuals.
The banks are also required to submit to tax authorities every month a list of transfers from customers to foreign organizations.
The decree had earlier received mixed responses from lawmakers. Pham Thi Thu Trang, a National Assembly deputy from the central province of Quang Ngai said that the decree contradicts regulations on personal information security and should not be imposed.
Another lawmaker, Bui Thi Quy Tho, supported the new decree but proposed that transaction fees be reduced to boost cashless spending and better tax management.
Vietnam is trying to tighten its tax policies as e-commerce booms as foreign service providers like Netflix expand their reach in the country.
An official of the General Department of Taxation said last month that, in Hanoi alone, there were over 18,300 organizations and individuals making a total of VND1.46 trillion ($62.9 million) from online sales via Google, Facebook, and YouTube in Hanoi alone, according to data from 45 commercial banks.
The department had collected nearly VND14 billion from them, the official said but did not mention the time frame for the figures.