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