woocommerce/templates/emails/plain/customer-invoice.php

<?php
/**
 * Customer invoice email (plain text)
 *
 * This template can be overridden by copying it to yourtheme/woocommerce/emails/plain/customer-invoice.php.
 *
 * HOWEVER, on occasion WooCommerce will need to update template files and you
 * (the theme developer) will need to copy the new files to your theme to
 * maintain compatibility. We try to do this as little as possible, but it does
 * happen. When this occurs the version of the template file will be bumped and
 * the readme will list any important changes.
 *
 * @see https://docs.woocommerce.com/document/template-structure/
 * @package WooCommerce/Templates/Emails/Plain
 * @version 3.5.0
 */

if ( ! defined( 'ABSPATH' ) ) {
	exit;
}

echo '= ' . esc_html( $email_heading ) . " =\n\n";

/* translators: %s: Customer first name */
echo sprintf( esc_html__( 'Hi %s,', 'woocommerce' ), esc_html( $order->get_billing_first_name() ) ) . "\n\n";

if ( $order->has_status( 'pending' ) ) {
	echo sprintf(
		/* translators: %1$s Site title, %2$s Order pay link */
		__( 'An order has been created for you on %1$s. Your invoice is below, with a link to make payment when you’re ready: %2$s', 'woocommerce' ),
		esc_html( get_bloginfo( 'name', 'display' ) ),
		esc_url( $order->get_checkout_payment_url() )
	) . "\n\n";

} else {
	/* translators: %s Order date */
	echo sprintf( esc_html__( 'Here are the details of your order placed on %s:', 'woocommerce' ), esc_html( wc_format_datetime( $this->object->get_date_created() ) ) ) . "\n\n";
}
echo "=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=\n\n";

/**
 * Hook for the woocommerce_email_order_details.
 *
 * @hooked WC_Emails::order_details() Shows the order details table.
 * @hooked WC_Structured_Data::generate_order_data() Generates structured data.
 * @hooked WC_Structured_Data::output_structured_data() Outputs structured data.
 * @since 2.5.0
 */
do_action( 'woocommerce_email_order_details', $order, $sent_to_admin, $plain_text, $email );

echo "\n=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=\n\n";

/**
 * Hook for the woocommerce_email_order_meta.
 *
 * @hooked WC_Emails::order_meta() Shows order meta data.
 */
do_action( 'woocommerce_email_order_meta', $order, $sent_to_admin, $plain_text, $email );

/**
 * Hook for woocommerce_email_customer_details
 *
 * @hooked WC_Emails::customer_details() Shows customer details
 * @hooked WC_Emails::email_address() Shows email address
 */
do_action( 'woocommerce_email_customer_details', $order, $sent_to_admin, $plain_text, $email );

echo esc_html__( 'Thanks for reading.', 'woocommerce' ) . "\n\n";

echo "\n=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=\n\n";

echo esc_html( apply_filters( 'woocommerce_email_footer_text', get_option( 'woocommerce_email_footer_text' ) ) );