A company identification number is a number assigned to the business upon start-up to identify this business for federal taxing and legitimacy. The number is the corporate equivalent to a Social Security number, as reported by the Small Business Administration.
The number is assigned by the Internal Revenue Service. A company's identification number consists of four to six digits. The number should always be located on a company's website. The ID number is typically referred to as a Federal Tax Identification number. The number is also used to create a business' credit file. Without an identification number, a company is not considered a legitimate business, as stated by the Internal Revenue Service.