The earliest known published reference to this explanation occurs
Philadelphia, Pennsylvania, U.S.
When this was recorded in the financial records, once-common accounting practices would use red ink to show negative amounts and black ink to show positive amounts. Black Friday, under this theory, is the beginning of the period when retailers would no longer be "in the red", instead taking in the year's profits. The earliest known published reference to this explanation occurs in The Philadelphia Inquirer for November 28, 1981.