When customers make an order in store, sales staff enters the details for a sales invoice into the sales computer system. The sales system then sends the details of the sales invoice to the inventory management system. The warehouse staff uses this information to prepare delivery documents. Customers are required to sign a paper copy of the delivery document upon receipt of the furniture. Sales invoices and delivery documents are serially numbered. The original copy of the customer-signed delivery document is then sent to the accounting department while the warehouse staff keeps a duplicate copy of the document. At the end of each day, the warehouse manager gives authorisation in the inventory management system to process sales transactions for which delivery has been made. The system then updates the perpetual inventory records and sends the sales transactions to the accounting system. The accounting staff checks the online sales invoices, but do not verify these against the signed delivery documents, before giving authorisation for the accounting system to record the sales in the accounting records. A junior accounting staff member is required to regularly check recent sales transactions to see whether there are duplicate or missing sales invoice numbers, and whether each sales transaction has both a sales invoice number and a delivery document number. This staff member admitted that she only checks occasionally however because the system is so reliable and has been used by the firm for numerous years.

Question:

Identify internal controls in this paragraph?