Final answer:
The most important purpose of a turn-around document in a business context is to serve as a source document.
Step-by-step explanation:
The most important purpose of a turn-around document in a business context is to serve as a source document. A turn-around document is a form that has both input and output fields, allowing information to be collected and processed and then returned to the business. This type of document is commonly used in transactional processes such as order fulfillment, invoicing, and data entry.