Explorations on a theme: "What is a transaction? "

2.  Bookkeeping

(Hint: click the other triangles to navigate to the other slides.)

It is nearly universal in today's accounting systems, to record sales in double-entry accounting:

The mirror image is happening on the buyer's books:

These are mirror images of essentially the same transaction.  Maintenance of accounting records for the same transaction within Buyers' books and Sellers' books, are a duplication of work.