An invoice is a document that a seller provides to a buyer, detailing the products or services rendered. It typically includes information such as the seller's and buyer's contact details, a description of the items sold, the quantity, price, and the total amount due. Invoices serve as a formal request for payment and help keep track of sales and purchases. Invoices are important for both businesses and customers. For businesses, they help manage cash flow and maintain accurate financial records. For customers, invoices provide a clear record of what they owe and can be used for expense tracking or tax purposes.