About 900,000 registered companies do not file annual returns and are potential sources of money laundering, a top government official said on Saturday, as Finance Minister Arun Jaitley pitched for the country’s top anti-financial crime agency to be used “expeditiously” against tax cheats.

Revenue secretary Hasmukh Adhia said the Prime Minister’s Office had set up a task force to monitor these companies and “there is no reason for us to let such companies operate in India”.

Of 1.5 million companies registered in India, about 600,000 file their returns, including annual audited reports, with the ministry of corporate affairs. About half of them show zero income, official records show.

“We have given notices to some of them,” Adhia said in New Delhi at a function of the Enforcement Directorate (ED).

The Bharatiya Janata Party government has intensified its drive against tax evaders since its November 8 decision to scrap old 500- and 1000-rupee notes, a move Prime Minister Narendra Modi said was aimed at breaking the back of India’s black economy.

Cracking down on domestic shell companies, the government decided in February to take “harsh punitive” action including freezing the bank accounts used to launder money or evade taxes.

Shell companies are fronts used as conduits to convert illicit money into legal cash, and are central to money laundering operations.

Speaking at the same event, finance minister Jaitley said the revenue department and the ED had a “very important role to play” in India’s war against black money.

“There is an expectation of compliance (of tax rules) and in the event of non-compliance, there is the power of penalising that the ED has. This power has to be expeditiously used whenever violations are detected,” he said.

Jaitley also said money laundering, round-tripping, tax evasion and the creation of shell companies had become a “standardised practice” that was not difficult to detect in the age of technological advancements.

“Our target has to be to make sure India as it evolves from a developing to developed economy (also changes) from a tax non-compliant society to a highly-compliant society.”

Adhia said the demonetisation of high-value banknotes had revealed the different ways people use to launder money, including through multiple entries in shell companies.