Work with both New membership and Renewal.
At the last step of checkout - payment details page, there is a place to enter discount code.
By the way, NSA stands for National Seniors Australia, so this deal is for Senior Ozbargainers :)
My account also says, next year it will be renewed at $12.5 as well. No more hunting for half price renewal every year.
If my thinking is mature for my age, does that classify me as a senior?