blank letter of bill

例句：

1. 1. The banksent a blank letter of bill to thecustomer.
   银行给客户寄了一张空白的信函。
2. 2.The company issued a blank letter of billfor their new product launch.
   公司为新产品发布发行了一张空白的信函。
3. 3. Theinvoice was a blank letter of bill withno details on the goods or services provided.
   发票是一张空白的信函，上面没有关于提供的商品或服务的详细信息。