WASHINGTON — The Internal Revenue Service said Monday it is ending its decades-old policy of making unannounced home and business visits, in an effort to help keep its workers safe and to combat scammers who pose as IRS agents.

Effective immediately, revenue agents will no longer make unplanned visits to taxpayers’ homes and businesses “except in a few unique circumstances,” the Treasury Department said in a statement. The agency will instead mail letters to people to schedule meetings.

“Today’s announcement is the right thing to do, at the right time,” new IRS Commissioner Daniel Werfel told reporters on a call Monday.

The change ends “an era at the IRS,” he said, reversing a practice by revenue officers whose duties include visiting homes and firms to resolve taxpayers’ liabilities by collecting unpaid taxes and unfiled tax returns.

The agency in recent years has experienced more threats, in part tied to conspiracy theories that agents were going to target middle-income taxpayers more aggressively after the passage of a climate, health care and tax bill that provided $80 billion to step up tax collections.

In response, the agency last August announced a comprehensive review of safety at its facilities. And in May, the agency said it would begin limiting workers’ personal identifying information on communications with taxpayers.

The Treasury Department’s inspector general for tax administration said in a report that it was “concerned that taxpayers and anti-government or anti-tax groups with malevolent intent may use the Internet or social media to track down and identify IRS employees, their families, their homes, and personal information to threaten, intimidate, or locate them for physical violence.”

The National Treasury Employees Union, which represents IRS workers, commended the agency for ending unannounced visits.

”The officers we represent will continue to efficiently and effectively carry out their mission of helping taxpayers meet their lawful tax obligations through other means of communication,” union leader Tony Reardon said in an emailed statement.

The issue of home visits has been politically contentious this year.

Ohio House Republican Jim Jordan sent a letter to Werfel and Treasury Secretary Janet Yellen in March, asking why journalist Matt Taibbi received an unannounced home visit from an IRS agent shortly he gave testimony on Capitol Hill regarding his research into Twitter records.

Werfel said he thinks “the issues raised by unannounced visits, including ones that have been raised to us by the U.S. Congress, will be significantly mitigated” by the policy change.

The agency said an increase in scam artists posing as IRS agents also had created confusion about unannounced home visits.