This is fairly common practice in Australia, but not in many other countries (PNG allows sacrifice to super, most other countries do not provide for it at all).
Here is the info for PNG (for example):
http://www.smoothpaygold.com/public_html/files/gold/man/png.pdf (refer pages 11-12)
The Solomon Islands for example do not have any provision in legislation for sacrifice (even though you can set it up - it may not be permitted by the relevant tax authority):
We can you how to process salary packaging in SmoothPay for Solomon Islands, however it is my opinion that S5 Income Tax Act excludes any kind of pre-tax deduction (including education), and that your employee may well end up having to pay additional tax at the end of the year.
Such practices are permitted under Australian law, however we have yet to see any such provision for the Solomon Islands (and I checked the Income Tax Act to be sure). Their website is very light on details of exemptions (Nil) and does not consider ex-pats etc at all, so some official guidance is needed.
The rules for Australia are fairly straight forward:
or, if you need information about Novated Leases (applicable to Australia only):