If you are using one page checkout then you need to make a small modification in checkout.php

search for
--------------------------------------------
case 'setPaymentMethod':
echo $onePageCheckout->setPaymentMethod($_POST['method']);
--------------------------------------------
and change that to
------------------------------------------
case 'setPaymentMethod':
require('held_orders_process.php');
echo $onePageCheckout->setPaymentMethod($_POST['method']);
------------------------------------------

Demo URL : http://demo.cartzlink.com/demo1/

DEMO Admin URL : http://demo.cartzlink.com/demo1/admin/

Attached is checkout.php for reference - You can use that file as well

Thanks

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