In postwar Japan (1945-), conventionally,the name “Instructions for the Preparation of Financial Statements of Manufacturing and Trading Companies” has been shortened to “Instructions”. These “Instructions” are regarded as the starting point of postwar “business accounting principles”. However, many questions―such as “when, from whom to whom, by what route was it issued?” have been raised. This paper compares the“Instructions” to “Instructional Documentation” in order to find and clarify answers to these questions. As a result, the starting points of the postwar “business accounting principles” in relation to “Instructional Documentations” are clarified.