External credit enhancement 是外部信用加强的意思，在CFA考试中是有这个知识点的，那什么是外部信用加强呢？今天给你说说这个这知识点哦！
Surety bond (履约*): reimburse investors for any losses incurred if the issuer defaults, by an insurance company.
Bank guarantee（银行担保）: same as surety bond but by a bank.
Letter of credit（信用证）: promise to lend money to issuing entity for any cash flow shortfalls.
会有第三方的财务担保，或者说有担保人。常见的外部信用加强包括履约担保，银行担保和信用证：
履约承诺：有背书，相当于给发行的债券购买了保险，履约承诺和银行担保有些类似，都是发行人违约时会赔偿给债券持有者。两者的区别是银行担保是银行发行的，而履约担保是保险公司发行的。
银行担保：发行者违约，投资者可以找银行还款。
信用证：发行者违约，银行先把款借给发行者还款。现在信用证用的较少，因为提供信用证的信用机构的信用等级下降会造成金融危机。
那你知道CFA考试是怎么考这个知识点呢？小编给你看看！
例：Which of the following is least likely to be a form of internal credit enhancement associated with a corporate bond issue?
A.Debt overcollateralization
B. Letter of credit
C. Debt subordination
解析：B is correct，A letter of credit is a form of external credit enhancement in which a financial institution provides the issuer with a credit line to be used for any cash flow shortfalls related to its debt issue.
信用证是属于外部信用加强。
