When someone places an order on a WooCommerce site, unless it’s a virtual-downloadable product, the order never automatically completes. It waits for you to take more actions.
Now as you set up your clients sites, this might be something to consider so you can instruct them how to use it especially if they have a situation where they don’t need to have the sale not completed.
The WooCommerce Order Status Extension
Once you upload and activate the extension, you will find a single setting under your WooCommerce > Settings > General Options.
You have the choices to leave at the default of Virtual and Downloadable Orders, choose only Virtual Orders, activate it on all orders or turn it completely off.
It essentially turns off the processing status.
That is all you need to do. Once turned on, all orders will be automatically completed when the customer has made payment. But again, instruct your clients in case they need to toggle this off or on for any reason.(Obviously
So if you are interested, check it out here.