You don't need their EIN (like if they don't have one). You can use their SSN. Either one. They should give you a W9 form with it. So you can give them a blank W9 to fill out or ask them for one. Here is a blank one......
https://www.irs.gov/pub/irs-pdf/fw9.pdf
And for the next person do not pay them until you get their SSN or EIN.
