 Used when product added to invoice line items Allows invoice-specific messaging different from marketing description Data Source: _product_invoice_description post meta (string) Example: WordPress Content: "Professional web design service creating stunning responsive websites". Invoice Description: "Website Design Services - 5 custom pages, responsive design, SEO optimization" Purpose: Apply one or more tax rates to product for automatic tax calculation Checkboxes for each available tax rate Multiple selections allowed (product can have multiple tax rates applied) Shows tax name and percentage (e.g., "Sales Tax (10%)") Display: "No tax rates available" if none configured Tax rates configured separately in Invoice Settings Data Source: _product_tax_ids post meta (array of tax IDs/indices)