Final answer:
Valuing AR at net realizable value departs from the historical cost principle, reflecting the expected cash to be received and aligning with conservatism in accounting.
Step-by-step explanation:
Reporting Accounts Receivable (AR) at net realizable value is a departure from the historical cost principle in accounting. The historical cost principle dictates that assets should be recorded and reported at the original cost at which they were acquired. In contrast, valuing AR at net realizable value considers the amount of cash that a company expects to actually receive, which reflects potential losses from uncollectible accounts. This approach aligns with the conservatism principle, which suggests that expenses and liabilities should be reported as soon as possible, but revenue only when it is assured.