Barter, Exchange, "Trade-ins" and Foreign Currency Transaction. 2007 California Commercial Code Chapter 3.General Obligation And Construction Of Contract. The United Nations Convention on Contracts for the International Sale of Goods (CISG) is the law governing crossborder sale of goods transactions. When you buy goods from foreign sources, you become the importer. An international sales contract is an agreement between a buyer and a seller that identifies the parties in the transaction, the goods or services being sold. "Bill of Exchange" means any financial instrument common in international trade, such as drafts, bills of exchange, or trade or documentary acceptances. (e) When completing blanks in provisions or clauses incorporated in full text, insert the fill-in information in the blanks of the provision or clause. World Trade Organization Custom Valuation Agreement. A sales agreement is a contract between a buyer and a seller that details the terms of an exchange.