What Is a Federal Employer ID Number?

A federal employer ID number is issued by the Internal Revenue Service and used to identify a business entity. Any business who has employees, operates as a corporation or partnership, or withholds taxes on income or other wages of a non-resident alien needs an employer ID number, according to the IRS. Individuals who have a Keogh Plan, or are involved with non-profit organizations, trusts or estates also need a number, according to the IRS.

The preferred method of applying for an employer ID number is through the IRS website. The application is only for businesses based in the United States or its territories, explains the IRS. Application information is verified during an online session, and the number is issued immediately. The principal business owner must have a valid Social Security number or personal tax identification number to use the online application.

It is also possible to apply for a federal employer ID number by filling out a Form SS-4 application and faxing or mailing it to the IRS at the number or address indicated on the form. The ID number can be faxed back within four days. A mail application takes four weeks to process, notes the IRS.

As of 2015, international applicants may call 267-941-1099 between 6 a.m. and 11 p.m. Eastern time, Monday through Friday. The person calling must be authorized to receive the number and must be prepared to answer questions contained on the Form SS-4, states the IRS.