Magento 2 Auto Invoice & Shipment - Cynoinfotech
https://www.cynoinfotech.com/product/auto-invoice-and-shipment-magento-2-extension/
An invoice is generated automatically after the customer completes placing the order. Auto Invoice and Shipment Magento 2 extension saves time for creating manual invoices and payment transactions. This extension automatically generates invoices and processes shipments to customers after their order.