This study shows how, between 1661 and 1683, the culture of double-entry, mercantile accounting was central to Jean-Baptiste Colbert’s massive project of royal archive building in ancient régime France. Scholars have tended to see state archives as the products of learned and legal culture. The case of Colbert demonstrates that mercantile culture and commerce also made an essential contribution to archival development in the early modern period, as well as laying the foundation for state sponsored learning, science, industry, art, building, and administration. It illustrates how economic interest and financial management drove archive formation and organisation in the early modern era, correcting the dominant emphasis on techniques derived from scholarship.