An invoice is a document outlining the exchange of the seller’s product or service for the buyer’s payment. The term “invoice” is commonly used interchangeably with “receipt.” Essentially, they serve the same purpose – to document the price and terms of a sale or exchange of service. A more complex exchange will often be documented with an invoice, meaning the exchange may require itemized lists, special terms or transaction details. While the general invoice definition includes any record of transaction, the term is typically used in reference to a document with more complexity than a simple receipt.