A Texas Sample of an Irrevocable Letter of Credit — Sample of form which may be used in lieu of obtaining a surety bond is a legal document that is used to guarantee payment of a specified sum of money. It is offered by a financial institution, typically a bank, to a party in lieu of a surety bond. This form is irrevocable and must be paid out regardless of any changes in the agreement between the two parties that it covers. There are two main types of Texas Sample of an Irrevocable Letter of Credit — Sample of form which may be used in lieu of obtaining a surety bond. These are the Standby Letter of Credit and the Commercial Letter of Credit. The Standby Letter of Credit is used to guarantee payment for goods or services that have not yet been delivered, while the Commercial Letter of Credit is used to guarantee payment of goods or services that have already been delivered. Both types of letters of credit are legally binding documents that must be paid out regardless of any changes in the agreement between the two parties that it covers.