Documentary Credit、Clean Credi、Irrevocable L/C等都是贸易往来中所会涉及的信用证种类，而Irrevocable L/C所对应的是Revocable L/C，对比分析可知，前者所具有的实用性要高于后者，因此在外贸往来过程之中，使用后者所具有的效果更为显著一些，能够让贸易方的收益得到保障。
Irrevocable L/C所指的是什么呢?它所指的是交易双方指定某银行开出信用证之后，只要这一信用证处于有效期之内，如果没有获得相关当事人的认可，那么开出这一信用证的银行就不能够对其进行撤回，或者是对相关内容进行修改，只要交易方中的受益人所提供的相应单据符合其规定，该银行就要履行其应具有的责任。在欧美国家一般对其解释为“It means that the issuing bank can not amend or cancel the credit unilaterally without the consent of the beneficiary and the parties concerned within the validity period of the letter of credit once it has been issued. As long as the documents provided by the beneficiary meet the requirements of the letter of credit, the issuing bank must fulfil its payment obligations.”。在对外商贸往来过程之中，应该在相关的沟通之中对于信用证使用类型提出需求，一般而言都应选择对自己这一方最有利的类型，例如对于销售方而言Irrevocable L/C就是很适合使用的一种信用证类型。因此在信用证中对其一定要加深了解。
例：
Mr. Gibson
We are glad that you are interested in the decorative paintings produced by our company. According to your order list, we need 1000 abstract decorative paintings in the living room, 500 Nordic bedroom decorative paintings and 450 modern abstract decorative paintings in the living room. The price of decorative paintings is so high that we communicated before. We have no objection to the price. A 3% discount will be given.
You mentioned the use of revocable letters of credit in the course of trade, but because of the management requirements of our company in the course of business, it is stipulated that irrevocable letters of credit should be used in the course of the corresponding transactions, so it is unacceptable under the system for such letters of credit as you use, and we hope you will be able to do so at 10. The L/C will be converted into an irrevocable L/C by 30 January, and we will arrange shipment before 2 January after receipt of the L/C. At present, the company has sufficient supplies. We can arrange shipment at any time according to your actual needs. The transportation cost and insurance cost will be borne by you during the transaction. Because of the large quantity of decorative paintings sold this time, the style of the paintings can not be guaranteed to be consistent, and the final interpretation is at our disposal.
吉普森先生
很高兴贵公司对我公司所生产的装饰画感兴趣，根据贵方所给出的订货清单，需要1000幅客厅抽象装饰画，500幅北欧卧室装饰画以及450幅现代抽象客厅装饰画，装饰画价格如此前我们所沟通的贵，公司对于价格没有异议，我公司将给予3%的优惠。
贵公司提及在贸易过程中将使用可撤销信用证，不过由于我公司在经营过程之中所具有的管理需求，规定在相应交易过程中都需使用不可撤销信用证，所以对于贵方所使用的这种信用证方式根据制度无法接受，希望贵方能够在10月30日之前将信用证转换为不可撤销信用证，我方会在接到信用证之后在1月2日之前安排发货，目前公司货源充足，根据贵方的实际需求我方可随时安排发货。本次交易过程之中相关运输费用以及保险费用由贵方承担。此次所销售的装饰画由于数量较多，所以画品方面的样式无法保证一致性，最终解释权由我方所有。
如上案例回函之中，销售方重点提及了产品的样式，尤为重要的是提到了“You mentioned the use of revocable letters of credit in the course of trade, but because of the management requirements of our company in the course of business, the use of irrevocable letters of credit is required in the course of the corresponding transactions, so this form of letter of credit used by you is not acceptable under the system.” 在这其中重点指出了在交易过程中所收取的信用证必须是不可撤销信用证，在这方面没有任何协商的余地，由于该公司产品销售数量较多，而且受到了众多用户的关注，所以产品一向是供不应求的直接指出“We hope you will convert the L / C to irrevocable L / C by October 30th.”这一点指出了需求对方提供信用证的时间，如果超出这一时间，很有可能无法达成这笔交易。
当然在如上案例之中，前一部分是可以直接借鉴模仿的，不论在任何贸易领域中都同样适用，而对于模板的后一部分则不可以完全借鉴模仿，由于在外贸交易过程之中谁掌控了话语权，谁在整个交易过程中就能够主导交易，掌握话语权则是看其所生产的产品是否是热销产品，如果销售方处于主导地位，产品热销，就可以按照如上的模板提出信用证的需求，不过在实际的交易过程中，如果买方处于主导地位，那么卖方在相应交易证问题提出方面就应该含蓄一些，不能够照搬如上模板的后半部分，否则很有可能导致这笔交易失败。