Fast invoice factoring is a financial service where a business sells its outstanding invoices (accounts receivable) to a third-party company, known as a factor, in exchange for an immediate cash advance. The term "fast" highlights the key benefit of this process: providing rapid access to working capital, often within 24 to 48 hours, without having to wait for customers to pay their invoices, which can take 30, 60, or even 90 days.