What number is used by the federal government to identify the tax accounts of employers?

The correct choice is the Employer Identification Number (EIN). The EIN is specifically designed for the purpose of identifying tax accounts of businesses and employers in the United States. It is issued by the Internal Revenue Service (IRS) and is used in various tax-related processes, such as filing employer tax returns, reporting payroll taxes, and paying business taxes.

This number serves a critical role in the compliance of businesses with federal tax regulations, ensuring that the IRS can effectively track the tax obligations and payments of each employer.

The other options represent different types of identification numbers: the Social Security Number (SSN) is used primarily for individual identification and personal tax purposes; the Adoption Taxpayer Identification Number (ATIN) is used for children in adoption situations to claim tax benefits; and the Individual Taxpayer Identification Number (ITIN) is for individuals who are not eligible for an SSN but need to file tax returns. These numbers do not function in the same capacity as the EIN when it comes to identifying employer tax accounts.