The IRS plans to go after 125,000 high-income earners who did not file tax returns going back to 2017 — and the agency says hundreds of millions of dollars of unpaid taxes are involved in these cases.

Beginning this week, the IRS will start sending out noncompliance letters to more than 25,000 people who earn more than $1 million per year and 100,000 people with incomes between $400,000 and $1 million who failed to pay their taxes between 2017 and 2021.

The campaign announced Thursday is part of the agency's ongoing effort to pursue high wealth tax cheats — mandated in part by funding provided through Democrats' Inflation Reduction Act passed into law in 2022 and a directive from Treasury Secretary Janet Yellen to IRS leadership not to increase audit rates on people making less than $400,000 a year annually.

"When people don't file a tax return they're required to, it's not fair to those hardworking taxpayers who responsibly do their civic duty under the laws of our nation," IRS Commissioner Daniel Werfel told reporters Thursday morning.

"And when people don't file their taxes, they need to know there's a consequence."

The IRS in recent months has announced a slew of new campaigns aimed at targeting high-wealth individuals who misuse the tax system or fail to pay their obligations.

For instance, last week IRS leadership said the agency will start up dozens of audits on businesses' private jets and how they are used personally by executives and written off as a tax deduction. And earlier this year, the agency announced it had collected roughly half a billion dollars in overdue taxes from delinquent millionaires.

Werfel said the agency's non-filer programs have only run sporadically since 2016 due to lack of funding and staffing. But since the federal tax collector received resources from the IRA, "the IRS now has the capacity to do this core tax administration work," he said.

"This isn't a small group of people we're talking about."