In the United States, an employer identification number, or EIN, is a distinct numerical digit issued by the Internal Revenue System to business establishments, according to the IRS website. It is the corporate counterpart to an individual's Social Security number, or SSN, which is issued by the Social Security Administration.
The EIN is written in a nine-digit standard format which is broken down into two parts: a two-digit prefix and a seven-digit serial number. The prefix signifies the code for which IRS campus issued the EIN.
Aside from using the EIN to distinguish business organizations, this number is also used by estate and trust companies that are legally compelled to disclose their earnings. The EIN also provides a convenient method for identifying and resolving conflicts in documentation between the IRS and SSA, notes the Official Social Security Website.