This is the screen used to create and edit supplier invoices.

The header fields are as follows:
Start Time - the date on which the invoice was created
Amount - the amount of the invoice - this is the sum of the line item amounts
Printed - this checkbox will be checked when the invoice is printed
Status - is initially set to In Progress, and can also be set to On Hold or Finalised

The Items tab allows you to add, delete, view and edit the line items. The fields are as follows:

Date - the date on which the line item was created
Product - the product - note that this is our product name, as opposed to the supplier's (given by Reorder Code and Description). Note also that there is no check that the product selected is in fact provided by the currently selected supplier.
Quantity - the quantity
Unit Price - the unit nett tax-excluded price of the item
Tax - the total tax payable for this line item
Total - the total line item amount - this will equal the Quantity times the Unit Price plus the Tax.