发票金额与超支
如前所述，发票金额计算的一个非常重要的目的是凭以付款结算。然而，实务中，付款金额或支款金额，可能与发票金额一致，也可能不一致。但无论如何，支款金额，理应以信用证金额，即信用证下允许支款的最高金额为限。否则，便构成了超支。
这样，发票金额与信用证金额，可能不同，通常情况下会等于或小于信用证金额，偶尔则会大于信用证金额。
那么，发票金额大于信用证金额，可以接受吗？

UCP600第18条b款：
A nominated bank acting on its nomination, a confirming bank, if any, or the issuing bank may accept a commercial invoice issued for an amount in excess of the amount permitted by the credit, and its decision will be binding upon all parties, provided the bank in question has not honoured or negotiated for an amount in excess of that permitted by the credit. 按照指定行事的指定银行、保兑行（如有）或开证行可以接受金额大于信用证所允许金额的商业发票，其决定对各有关方均有约束力，只要该银行对超过信用证允许金额的部分未作承付或者议付。

上述规定表明：
- 按指定行事的指定银行，以及保兑行、开证行，可以接受发票金额大于信用证所允许的支款金额，并不因此产生不符点。对于相关银行来说，这是一种权利。换句话说，银行没有义务必须接受发票金额大于信用证所允许的支款金额，只是一旦接受则并不因此产生不符点。国际商会在R419的咨询2的分析及结论中说：It can be seen that a bank is under no obligation to accept an invoice for an amount which is greater than the L/C amount, but if the nominated bank elects to do so it binds all other parties, provided the settlement to the beneficiary is no greater than the value of the credit. It would be expected that a nominated bank would accept such invoices. An invoice that shows a deduction due to a ‘discount’ being granted would not be a reason, in itself, to reject the documents.