Historians of the origins of modern accounting have generally accepted that the earliest known instructional treatise on double entry bookkeeping was the one published by Luca Pacioli in 1494. This paper dispels that view, presenting detailed evidence of an earlier bookkeeping manual from 1475 that has hitherto remained virtually unknown. Using evidence gathered from the text, the paper on which it is written, and the handwriting, this paper speculates on its origins. It also presents an overview of the material taught in that book and compares it with other texts on double entry published up to the mid-16th century. In the course of doing so, a generic bookkeeping curriculum for the period is identified and specialist topics included in the manual from 1475 are noted and discussed. Finally, this paper considers the place of this text in the history of accounting, accounting practice, and accounting education. It concludes that this manual is of major significance in providing insights into how accounting was taught in 15th century Venice, and of which aspects of business it was felt that instruction in double entry was of fundamental importance at that time.