Employer Identification Number

The Employer Identification Number (EIN), also known as the Federal Employer Identification Number (FEIN) or the Federal Tax Identification Number, is a unique nine-digit number assigned by the Internal Revenue Service (IRS) to business entities operating in the United States for the purposes of identification. When the number is used for identification rather than employment tax reporting, it is usually referred to as a Taxpayer Identification Number (TIN), and when used for the purposes of reporting employment taxes, it is usually referred to as an EIN. These numbers are used for tax administration and must be not used for any other purpose. For example, the EIN should not be used in tax lien auction or sales, lotteries, etc.

Similar in purpose to the Social Security number assigned to individuals, EINs are used by employers, sole proprietors, corporations, partnerships, non-profit organizations, trusts and estates, government agencies, certain individuals and other business entities. The IRS uses this number to identify taxpayers that are required to file various business tax returns. Individuals who are employers may choose to either obtain an EIN or use their Social Security number for the purpose of reporting taxes withheld on behalf of their employees. Contrary to some misconceptions, credit bureaus and credit issuers can tell the difference between SSNs and EINs. SSNs can be validated as to origin and state/year of issuance. The credit bureaus and issuers are highly trained in fraud detection, and increasingly sophisticated algorithms and protections are used. This is why the EIN is not considered sensitive information, and is freely distributed by many businesses by way of publications and the internet.

The EIN system was created by the IRS in 1974 by Treasury Decision (TD) 7306, 39 Fed. Reg. 9946 . The authority for EIN's is derived from 26 USC 6011(b), requiring taxpayer identification for the purpose of payment of employment taxes. The provision was first enacted as part of the revision of the Tax Code in 1954. This authority was broadened in 1961 by 26 USC 6109. An EIN is usually written in the form 00-0000000 whereas a Social Security Number is usually written in the form 000-00-0000 in order to differentiate between the two. There are EIN Decoders on the web that can identify in what state the company registered the EIN.

...
Wikipedia