The nouns:

• Invoice
• Address
• LineItem
• Product
• Description
• Quantity
• Price
• Total
• AmountDue

Description and Price are properties (data members) of the Product class.

Total and AmountDue are computed values rather than classes or data members.

This leads to candidate classes:

• Invoice
• Address
• LineItem
• Product

Each of these represents a useful concept for the problem. Make each one a class.