A Maryland Irrevocable Letter of Credit (IOC) is a financial instrument which functions as a guarantee of payment for an underlying contract. It is issued by a third-party financial institution, usually a bank, and is typically used in large-scale transactions such as international trade or real estate deals. An IOC is essentially a promise of payment from the issuer to the beneficiary if certain conditions are met. The IOC is irrevocable, meaning it cannot be altered or cancelled without the consent of all parties involved. There are two primary types of Maryland Irrevocable Letters of Credit: Standby Letters of Credit (SLOC) and Commercial Letters of Credit (CLOCK). An SLOC is a guarantee of payment in the event of a default on the underlying contract, and a CLOCK is a guarantee of payment for goods and services delivered according to the terms of the contract. Both types of Blocs must meet the requirements of the Uniform Commercial Code in order for them to be legally enforceable.