If you want to make coupon code as a required field, this plugin will help.
During checkout when a customer will try to place an order without entering any coupon code, checkout process will be interrupted and customer will see an error notice.
You can configure the error notice text from "WooCommerce>Force Coupon" menu from admin panel.
From your WordPress dashboard
- Visit 'Plugins > Add New'
- Search for 'Force Coupon for WooCommerce'
- Activate 'Force Coupon for WooCommerce' from your Plugins page.
From
WordPress.org
- Download 'Force Coupon for WooCommerce'.
- Upload the 'woo-force-coupon' folder to your '/wp-content/plugins/' directory, using your favorite method (ftp, sftp, scp, etc...)
- Activate 'Force Coupon for WooCommerce' from your Plugins page.
After that you can configure the plugin settings from "WooCommerce>Force Coupon" menu from admin panel.