The following deficiency finding is included in an interim audit report prepared during the course of the audit:
Controls over the billing of charges for parts-repair work.
Current procedures provide for using prenumbered sales order forms and recording sales orders for repairs in manually maintained logs. These procedures also provide for creating manually serialized shipping documents.
These shipping documents are recorded in the sales order log, which closes the sales order and may give rise to a billing for the repair work. (Some work is done on a "no-charge " basis. Our examination of the sales order log disclosed a significant number of sales order numbers unmatched by shipping document numbers for the past two years. As a result, it is uncertain whether the repair work performed for those orders had been authorized. Specifically, we found that the sales order logs showed "no entry"
for 71 (about 18%) sales order serial numbers spread randomly- over a range of about 400 serial numbers covering a recent twelve-month period. This indicated that billing personnel had not received sales orders for, or information about, the disposition of those serial numbers. Further investigation disclosed that 50 of the serial numbers showing "no entry" related to sales orders which had been voided or related to billings which had been closed at no charge. In addition, 16 other serial numbers related to sales orders which, in fact, were issued and were still open. However, we were unable to account for the remaining 15 serial numbers. The interim report contains errors made by the internal auditor. The errors involve numbers, computations, and logic.
Required: 

Identify three errors made by the internal auditor and state how vou would correct each one.