Do sole proprietors have to get an EIN or can they use SSN?

It's optional.  But you need an EIN if you pay employees.  You might want to get an EIN so you don't have to give out your ssn like if you pay any sub contractors and need to issue them a 1099NEC.  Or if someone pays you over 600 and wants to give you a 1099NEC to report the income.

Here is some IRS reading material……

IRS information on Self Employment

http://www.irs.gov/Businesses/Small-Businesses-&-Self-Employed/Self-Employed-Individuals-Tax-Center

Pulication 334, Tax Guide for Small Business

http://www.irs.gov/pub/irs-pdf/p334.pdf

Publication 535 Business Expenses

http://www.irs.gov/pub/irs-pdf/p535.pdf

Publication 463 Travel, Gift, and Car Expenses

https://www.irs.gov/pub/irs-pdf/p463.pdf

A sole proprietor with no employees is not required to get an EIN. But if you have employees then the EIN is required.

Even without employees it would be a good idea to get and use an EIN. When vendors or clients who pay you are required to issue you a 1099, they need either your SSN or EIN in order to do that. I to am a single owner business with no employees. I have and use an EIN for my business because there's no way on this green earth that I am ever giving my SSN out to a vendor or client. They get my EIN, or we just don't do business.

For those that you pay where you are required to issue a 1099, it's highly advised you have them provide you a completed W-9 form before you pay them anything. That way, come tax filing time if you are required to issue a 1099, you have the information necessary to do so. You can get a blank W-9 form at https://www.irs.gov/pub/irs-pdf/fw9.pdf

if you issue 1099s I would definitely get an EIN so your not giving out your SSN to a bunch of strangers,

Also, your sole proprietorship must obtain an EIN if it plans to have a SEP-IRA or an individual 401K.