Partial Invoices & Refunds

Product Fees are stored on sales items and are automatically prorated by quantity for invoices and credit memos.

Partial Invoices

When creating an invoice for a subset of ordered quantity, fee amounts are calculated as:

fee_on_invoice_item = fee_on_order_item * (invoiced_qty / ordered_qty)

The prorated values are written to invoice item fields:

• base_productfee_amount, productfee_amount
• base_productfee_tax_amount, productfee_tax_amount
• productfee_applied_json, productfee_tax_json (copied from order item snapshot)

Partial Refunds (Credit Memos)

Credit memos use the same ratio logic:

fee_on_creditmemo_item = fee_on_order_item * (refunded_qty / ordered_qty)

This keeps fee totals consistent across multiple partial invoices / refunds.