Products can be quickly added to invoices in two ways: Product Lookup - Invoice editor includes product search/lookup field that searches all products by title and price Manual Line Item - Create line items manually with custom amounts and descriptions When a product is added to an invoice: Product name, price, and description are copied to invoice line item Applied tax rates automatically included for tax calculation Merchant company from product used for invoice company reference Multi-currency prices calculated based on invoice currency settings Link to product maintained for reference (edit link optional)