Sole proprietor , used SSN, now i have and EIN, which to file with?

As a sole proprietorship the Form 1040 Schedule C or Schedule C-EZ that you are required to file generally includes the owner's Social Security Number (SSN)    

You will use your SSN rather than your Employer Identification Number (EIN).  The EIN for a sole proprietorship is generally used to file and provide information statements (e.g 1099-MISC or W-2 etc.) The statements have separate filing requirements than your Form 1040 business returns and are treated as separate issues by the Internal Revenue Service.

Just to be sure I understand correctly: as a sole proprietor, regardless of whether the multiple 1099s I receive use my SSN or EIN, all the income is combined on one Schedule C for which I would use my SSN and not EIN?

Thanks.

As long as the LLC is a single-member LLC and income is from the same "business/activity" - that is correct. 

If it's a multi-member LLC, you will need to file an entity return and you need a TurboTax Business program for that. 

If it's income from more than one type of business, then you will need to report it on more than 1 Schedule C. 

Thanks for the quick reply.

I actually don't have an LLC altogether—still a sole-proprietorship but just applied for an EIN so I can create a Solo 401(k).  I just wasn't sure if that meant that I now had to file two Schedule Cs and that income for SSN-based 1099s would have to be tracked separately from EIN-based 1099s—which would also impact how much I can contribute to the Solo 401(K).

Though it sounds like for my practical purposes the SSN and EIN would be rather interchangeable—I can open the Solo 401(k) with the EIN; I don't need to bother updating W9 forms with existing clients; and I can use the EIN on W9s moving forward for future clients.