Abstract: Article 78 of The United Nations Convention on Contracts of International Sales of Goods (viz. CISG) only provides a general principle for interest payment in the situation that the creditor delays for payment, but without specific method for the calculation of interest rate, which leads to tremendous divergence in the practice when the different arbitration organs in different countries applies Article 78 of CISG. Obviously, this vague stipulation would reduce the unified value of the Convention and is the greatest flaw of the CISG. Such a missing of the method to determine the interest rate is a kind of loophole beyond the Convention and should be settled within the framework of the Convention by firstly quoting the general principles of the CISG. If the specific amount of interest rate still cannot be determined, then the relative stipulations in international private laws can be applied, generally, the interest rate of commercial loans at the country of the business location of the debtor should be taken as the standard for the delayed interest.

Key words: loophole beyond the law; loophole in the law; full compensation principle; principle of reason