Final answer:
A summation of customer account numbers from a batch of sales invoices is a hash total, which serves as an internal control or error detection mechanism.
Step-by-step explanation:
The summation of customer account numbers from a batch of sales invoices would be classified as a hash total. A hash total is a control total that does not necessarily have a logical meaning in the context of the business operation itself but is used for internal control or error detection purposes. In this case, customer account numbers are essentially non-financial data, and the sum of these numbers is used to ensure that a batch has been processed correctly without any omissions or duplications.