An Employer Identification Numbers, or EIN, is assigned by the Internal Revenue Service in order to identify a business entity. It is also called a Federal Tax Identification Number and is used on tax forms.
Employer Identification Numbers are issued for free to a business, which is formed legally before applying. A business requires an Employer Identification Number when it has employees, operates as a partnership or corporation or has a Keogh plan, in addition to several other reasons.
A business can apply for an Employer Identification Number online, by fax or by mail. If applying online, an EIN is received immediately. Effective as of May 21st, 2012, issuance of an Employer Identification Number is limited to one per responsible party per day.