$cart->trans_type = ST_SALESINVOICE;
$cart->reference = $Refs->get_next($cart->trans_type);
$invno = $cart->write(1);
+ if ($invno == -1)
+ {
+ display_error(_("The entered reference is already in use."));
+ display_footer_exit();
+ }
update_last_sent_recurrent_invoice($tmpl_no, $to);
return $invno;
}