from 1099-S instructions
If no closing disclosure is used the person responsible for closing the transaction is the one who files the 1099-S, in the following order:
apparently, one attorney is going to represent both parties at the closing so it's him or her so a) and b) would be the same
a. The transferee's attorney who is present at the delivery of
either the transferee's note or a significant part of the cash
proceeds to the transferor or who prepares or reviews the
preparation of the documents transferring legal or equitable
ownership;
b. The transferor's attorney who is present at the delivery of
either the transferee's note or a significant part of the cash
proceeds to the transferor or who prepares or reviews the
preparation of the documents transferring legal or equitable
ownership
