You must obtain an employer identification number (EIN) if you do any of the following:
 

	Form a C or S corporation or partnership.
	Pay wages to one or more employees.
	File pension or excise tax returns.

If you are a sole proprietor without employees, getting an EIN is not required as long as you report the financial results of your business on Form 1040, Schedule C.

In that case, the IRS and the Social Security Administration use your social security number to track income tax and self-employment tax, and to maintain your earnings record.