Select an existing product by clicking on the dropdown arrow to
the right of the Item field to show the list of existing products
The invoice item fields - description, quantity, each and VAT
(if shown) will be filled with the details from the existing
Click in the fields to make the desired changes, i.e. to change the
Quantity, Each, Discount or VAT fields.
Note: You can also
search for products to insert on an invoice. See Search for a
Product for more information.