Private Sales - Need to Document That FFL Transfer Was Done??

Question for anyone who has done a private sale with FFL Transfer, does the seller receive anything from the FFL to show that they followed the law, is there any need to be able to prove that you did? In past I always got a BOS from buyer, now not sure if I need to do something else to cover myself

The FFL should be giving you, the Seller, an FFL transfer sheet that shows the FFL took possession of the firearm to conduct the transfer to the Buyer.

That should be sufficient documentation to prove proper, lawful compliance.