A proforma invoice is a preliminary document issued by a seller to provide a detailed estimate of a transaction before shipment. It outlines product details, prices, and payment terms, serving as a quotation rather than a demand for payment. Unlike a commercial invoice, it is not legally binding but can assist in customs clearance or financing. Businesses use proforma invoices to ensure clarity in trade agreements and avoid disputes. Understanding its purpose and key features is essential for smoother international transactions.