What was sold? Do you need to have buyer and seller both complete 8594? 

Schedule B only requires SSN when it is seller financed interest for a PERSONAL RESIDENCE. Even then, if the buyer doesn't care about deducting the mortgage, why should we care? 

If it is interest on a rental, then the buyer probably should be issuing a 1099 to the seller, so again, why should we care?

EDIT - I have added a photo of the ceiling over my desk that I often used for basis calculations.