Final answer:
Reconciling control totals for sales invoices with the accounts receivable subsidiary ledger is the least likely internal control to reduce billing errors, as it focuses on ledger accuracy post-invoicing.
Step-by-step explanation:
The internal control activity that is least likely to reduce the risk of errors in the billing process among the options provided is reconciling the control totals for sales invoices with the accounts receivable subsidiary ledger. This activity is essential for ensuring that all billed sales are appropriately recorded and reflected in the accounts, but it does not directly address prevention or detection of errors in the billing process itself. Instead, this control is more related to the accuracy and completeness of the ledger postings after invoices have been issued.
A typical internal control procedure designed to reduce billing errors is a preventative control, such as comparing shipping documents with corresponding sales invoices, using automated controls to ensure pricing accuracy, or matching shipping documents with approved orders before generating an invoice. These controls are established to detect and prevent errors at the source before the transaction is recorded in the financial system.