Can a sole proprietor have an employer identification number?
A: Yes. In fact, it's encouraged to help guard against identify theft.
For example, if you're a sole proprietor and you must issue Form 1099-MISC to an unincorporated independent contractor (required for each unincorporated contractor you paid $600 or more), there's a box on Form 1099-MISC where you must enter your federal identification number. A federal identification number may be your social security number or a federal Employer Identification Number (EIN).
By using your EIN on Form 1099 instead of your social security number, you'll prevent the recipient(s) of this form from having access to your social security number. Although the word "Employer" is part of the name of this identification number, you don't actually have to be an employer to get an EIN.