Control which Paid WooCommerce Orders are Automatically Completed
WooCommerce automatically completes orders for virtual-downloadable products after successful payment, but it won’t autocomplete other orders, as you may need to take actions between when the order is processed and completed. If you sell shippable products, you probably need to ship them before completing the order. If you sell virtual products like services, you probably have to do something between when the order is paid and completed.
