This can be related to 2 different things: High-Performance Order Storage is enabled: Note that High-Performance Order Storage (HPOS) is now enabled by default. If HPOS is enabled, you need to use instead a compatible hook, like: add_action('woocommerce_checkout_create_order', 'save_custom_form_data_to_order'); function save_custom_form_data_to_order( $order ) { if ( isset($_POST['custom_form_data']) ) { $order->update_meta_data( 'custom_form_data', sanitize_text_field($_POST['custom_form_data']) ); } } Or you could use alternatively the following (requires using the save() method): add_action('woocommerce_checkout_order_created', 'save_custom_form_data_to_order'); function save_custom_form_data_to_order( $order ) { if ( isset($_POST['custom_form_data']) ) { $order->update_meta_data( 'custom_form_data', sanitize_text_field($_POST['custom_form_data']) ); $order->save(); } } With HPOS, WordPress Post meta functions doesn't work any more as WooCommerce orders use custom database tables for better performances. So HPOS requires to use WC_Data, WC_Abstract_Order or WC_Order methods on the WC_Order object. So to get/read the value from your custom field, you will use something like: $order = wc_get_order( $order_id ); // If needed get the WC_Order object $value = $order->get_meta('custom_form_data'); // Get custom field value Checkout Blocks is enabled: Note that Checkout Blocks is now enabled by default, and only allows very few customizations. The following action hooks won't work when using Checkout Blocks: woocommerce_checkout_create_order (compatible with HPOS) woocommerce_checkout_update_order_meta woocommerce_checkout_order_created (compatible with HPOS) and many more… The alternative is to switch back to legacy classic Checkout (shortcode).