An invoice is a commercial document issued by a seller to a buyer, relating to a sale transaction and indicating the products, quantities, and agreed prices for goods or services rendered. Specifically, an invoice for self-employed individuals is a document that details the goods or services provided, the agreed-upon price, and the payment terms. For example, a freelance writer may issue an invoice to a client for the completed writing services, outlining the number of articles written, the agreed-upon rate, and the payment due date.
Invoices are essential for self-employed individuals as they provide a record of income and expenses, facilitate the tracking of payments, and establish clear payment expectations with clients. The use of invoices has a long history in commerce, dating back to ancient civilizations, and has evolved over time to become a standard practice in business transactions.