The IRS initiates most contacts through regular mail delivered by the United States Postal Service.

However, there are special circumstances in which the IRS will call or come to a home or business, such as when a taxpayer has an overdue tax bill, to secure a delinquent tax return or a delinquent employment tax payment, or to tour a business as part of an audit or during criminal investigations.

To understand how and when the IRS contacts taxpayers and determine if it’s truly the IRS, review this article: https://www.irs.gov/uac/newsroom/how-to-know-it-s-really-the-irs-calling-or-knocking-on-your-door?