Final answer:
The best documentation tool for an accountant to use for mapping an accounting information system in terms of data entry, storage, and output is a system flowchart.
Step-by-step explanation:
Nishant Kumar, who has been hired as a staff accountant for American Manufacturing, is tasked with documenting the existing accounting information system (AIS). To understand the AIS thoroughly, including data entry, storage, and output, the appropriate documentation tool to utilize would be a system flowchart.
This tool will allow him to visualize the entire process of the AIS, examining how information is processed and flows through the system. A system flowchart will effectively demonstrate the interrelationships between data processing steps, hardware, and the various system components and provide a detailed view of the operational flow of the system, making it ideal for Nishant's objective to make recommendations for improvements.