Final answer:
The primary purpose of an invoice form report with a drop-down list of invoice numbers is to show the invoice number and date.
Step-by-step explanation:
The primary purpose of an invoice form report with a drop-down list of invoice numbers is to show the invoice number and date.
This feature allows users to select a specific invoice number from the drop-down list and view the corresponding details for that specific invoice, including the date it was issued.
By selecting an invoice number, users can easily access specific invoice information without having to search through a large database or manually inputting the invoice number.