What document is sent to the buyer when the seller does not know the buyr and is unsure whether he will receive payment?

The document typically sent to the buyer in such situations is a "pro forma invoice." This invoice outlines the details of the goods or services offered, including pricing and terms, but is not a formal request for payment. It serves as a preliminary agreement and helps establish the buyer's intent, allowing the seller to gauge interest and potentially secure payment before finalizing the transaction.