The IRS released the formal notice on Wednesday.

"We encourage those Americans who can file their taxes to continue to file their taxes on April 15, because for many Americans, you will get tax refunds," he said Tuesday in a news conference.

If you owe a payment to the IRS, you can defer up to $1 million as an individual, Mnuchin said. "The reason we're doing $1 million is that covers lots of pass-throughs and small businesses and $10 million to corporations — interest free and penalty free for 90 days," he said.

Barry Melancon, president and CEO of AICPA, said that while the administration is allowing certain taxpayers to delay tax payments for 90 days and is providing interest and penalty relief, "unfortunately, this important payment relief does not apply to the filing of tax returns. The concern and confusion related to coronavirus is causing cities across the country to shut businesses down, and Treasury's recent decisions do not reflect the real-world difficulties tax practitioners and their clients are experiencing."

Melancon stated that "it is impossible for every taxpayer and their tax adviser to prepare returns in this environment."

Nearly 60% of all taxpayers turn to a tax practitioner to prepare and file their tax returns, "and individual and business tax filing deadlines are fast approaching," he said.

"Even the relatively simple process of filing an extension form requires calculations based on data and information from the taxpayer. Given the current environment, this extension process is impossible for many taxpayers."

He called on Treasury to act immediately to extend the April 15 filing deadline and provide "more clarity on the details of recent relief actions."