Set invoice number when send invoice WC to Wave

functions.php

<?php
/**
 * Set Invoice number as order id
 *
 * @param array $variables get variables.
 * @param int $order_id get order id.
 * @return array
 */
function wave_order_variable( $variables, $order_id ) {

	$variables['input']['invoiceNumber'] = "$order_id";
	return $variables;
}
add_filter( 'venus_wc_export_invoice_variables', 'wave_order_variable', 10, 2 );