UPDATE
Revenue now require that P45s are only acceptable if printed on their stationery. The P45 printed from Payback is not acceptable.
P60s printed from Payback continue to be acceptable.
To produce a P45 on Revenue Stationery, you need to first upload the P45 to ROS. When you have successfully done this, a P45 PDF is sent to you ROS inbox that you can then print on Revenue Stationery.
More information here:
http://www.payback.ie/phpBB3/viewtopic.php?f=6&t=725and
https://www.ros.ie/info/faq/p45faq.html