What document signifies an agreement between two parties for future payment?

A contract is a legally binding document that signifies an agreement between two parties for future payment or the provision of goods and services. It outlines the terms and conditions agreed upon by the parties, including the specifics of what is to be delivered, the payment terms, and any other relevant conditions. This makes it foundational in establishing rights and responsibilities, ensuring that both parties are aware of their commitments and the consequences of failing to meet those obligations.

While a letter of credit is a financial instrument used primarily in international trade to guarantee payment, it does not itself signify an agreement between two parties; instead, it serves to facilitate payment when certain conditions are met. A purchase order is a document issued by a buyer to a seller, indicating the intent to purchase goods or services, but it does not create a formal legal agreement in the way a contract does. An invoice is a request for payment that outlines the amount due for goods or services already provided, but it does not signify an agreement; rather, it reflects the outcome of a previously established contract. Therefore, the contract is the correct answer as it directly represents the agreement for future payment between the parties involved.