What is an invoice, anyway? Simply put: it’s just an itemized list of goods shipped specifying the price and terms of sale. But it’s also a necessary artifact to organize and keep track of goods bought and sold. Maybe you sell aluminum to NASA since they need aluminum to fly into space, and you need a record of your transactions. Naturally, you use invoices: maybe they’re digital, maybe they’re paper. And because every company uses invoices, we can measure global trade and make sense of trends in commerce. Since our human penchant is to keep records, we can track the history of invoicing to the beginning of written language itself. Over the course of time, the way we’ve kept track of transactions has changed, reflecting the culture and technology of the era. From notches in a bone to EDI and beyond, we’re celebrating the past, present, and future of invoices.