Works for Bank issued AMEX cards. Register separately for both sites.
Register an eligible Card, spend $500.00 or more on that Card, in one or more transactions, online at between 23 September and 31 October 2014, and receive one $150.00 statement credit.
https://enroll.amexnetwork.com/AU/en/mr_porter_credit/
https://enroll.amexnetwork.com/AU/en/net-a-porter_credit/
All these AMEX deals, maybe I should get me a AMEX card.
Looks like a good deal, good find.