EINs are used to identify the tax accounts of employers, certain sole proprietors, corporations, partnerships, estates, trusts, and other entities.
If you don't already have an EIN, you need to get one if you:
1) Have employees,
2) Have a qualified retirement plan,
3) Operate your business as a corporation or partnership, or
4) File returns for:
a) Employment taxes, or
b) Excise taxes.
Applying for an EIN
You can get an EIN:
Online - Click on the EIN link at www.irs.gov/businesses/small. The EIN is issued immediately once the application infomration is validated.
By telephone at 1-800-829-4933 from 7:30 am to 5:30 pm in the applicant's local time zone.
By mailing or faxing Form SS-4, Application for Employer Identification Number (pdf).
When to Apply
You should apply for an EIN early enough to receive the number by the time you must file a return or statement or make a tax deposit. If you apply by mail, file Form SS-4 at least 4 to 5 weeks before you need an EIN. If you apply by telephone, you can get an EIN immediately. If you apply by fax, you can get an EIN within 4 business days.
If you do not receive your EIN by the time a return is due, file your return anyway. Write "Applied for" and the date you applied for the number in the space for the EIN.
More Than One EIN
You should have only one EIN. If you have more than one EIN and are not sure which to use, contact the Internal Revenue Service Center where you file your return. Give the numbers you have, the name and address to which each was assigned, and the address of your main place of business. The IRS will tell you which number to use.
For more information about EINs, see Publication 1635, Understanding Your EIN (pdf).
Information courtesy of the Internal Revenue Service.