Ahhh, its the Sale to a related party name box that's giving me the error....the property got sold to an uncle, he doesn't want to give up his SSN though  (there's huge family drama!).  

This real estate has been in the family for generations, owned by a bunch of different family members, all undivided ownership...they all had to sell or none of them could sell...they've been fighting over it for decades!  The uncle ended up buying out the family members that are my clients and they are carrying note.

I don't see many installment sales, how important is it whether we report it as a related party sale or not?