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A letter of credit is a document issued by a financial institution, or a similar party, assuring payment to a seller of goods and/or services.[1] The seller then seeks reimbursement from the buyer or from the buyer's bank. The document serves essentially as a guarantee to the seller that it will be paid by the issuer of the letter of credit regardless of whether the buyer ultimately fails to pay. In this way, the risk that the buyer will fail to pay is transferred from the seller to the letter of credit's issuer.The letter of credit also insures that all the agreed upon standards and quality of goods are met by the supplier.

Letters of credit are used primarily in international trade for large transactions between a supplier in one country and a customer in another. In such cases, the International Chamber of Commerce Uniform Customs and Practice for Documentary Credits applies (UCP 600 being the latest version).[2] They are also used in the land development process to ensure that approved public facilities (streets, sidewalks, storm water ponds, etc.) will be built. The parties to a letter of credit are the supplier, usually called the beneficiary, the issuing bank, of whom the buyer is a client, and sometimes an advising bank, of whom the beneficiary is a client. Almost all letters of credit are irrevocable, i.e., cannot be amended or canceled without the consent of the beneficiary, issuing bank, and confirming bank, if any. In executing a transaction, letters of credit incorporate functions common to giros and traveler's cheques.