Sole proprietors need to have an EIN only if they have one or more employees, if they have a Keogh plan, or if they are required to file excise tax forms such as those for sales tax, alcohol or tobacco.
If you purchase a business for which an EIN is needed, use your own EIN or get a new one--don't use the EIN of the previous owner. If you operate more than one business as a sole proprietor, you should use the same EIN for each one; if you operate businesses in forms other than sole proprietorship, you'll need a separate EIN for each business entity.
To apply for an EIN, you can file a paper Form SS-4, Application for Employer Identification Number, with the appropriate IRS Service Center for your state. If you apply by mail, it generally takes about four weeks to receive the number. If you need to file your tax return before you receive the EIN, write "applied for" in the space where the EIN should go.
The files are in Adobe Portable Document Format (.pdf), and you will need the free Acrobat Reader to view and print them.
Downloads:
Form SS-4, Application for Employer Identification Number
Instructions for Form SS-4, Application for Employer Identification Number