SS4
IRS form or application to apply for an EIN. This relays the contact information for the entity and the person responsible for requesting it. See EIN.
SSN (Social Security Number)
A nine-digit number assigned to citizens, some temporary residents and permanent residents of the United States (US) in order to track their income and determine benefit entitlements. US investors into an SPV need to share their SSN with the SPV Organizer for KYC/AML background check purposes. Read more: http://www.investopedia.com/terms/s/ssn.asp#ixzz4EK9E8Hmj