What is a sales invoice primarily used for?

A sales invoice serves a fundamental role in business transactions, primarily functioning as a formal request for payment for goods or services rendered. It includes essential details such as the quantity and description of items sold, the prices, applicable taxes, payment terms, and the total amount due. The invoice not only facilitates the collection of funds from customers but also provides a record of the transaction for both the seller and the buyer, thereby supporting financial transparency and accountability. This documentation is critical for effective cash flow management, as it helps businesses track outstanding receivables and ensure timely payments.

Each of the other choices pertains to different business functions. Documenting employee payroll is specific to HR and payroll management, summarizing annual sales data relates more to reporting and analysis rather than individual transactions, and reporting financial discrepancies typically involves error resolution, which is outside the scope of a sales invoice's purpose. Thus, the primary use of a sales invoice centers on facilitating the payment process for sold goods or services.