The term SEND AN INVOICE can be broken down into two crossword solutions: SEND and BILL. SEND is a verb meaning to cause something to go from one place to another, typically by post or email. An invoice is a document sent by a seller to a buyer, listing the goods or services provided and their cost. Therefore, the phrase SEND AN INVOICE means to SEND a document to a buyer that outlines the goods or services provided and their cost.