Redeem here https://www.msonlineservices.co.nz/
$25 Cashback comes as Prezzy Card
To receive your $25 Prezzy Card simply upload a picture of your invoice and redeem it from Microsoft's website no later than 10th September 2016. Proof of purchase must be submitted to be eligible for the $25 Prezzy Card. Your Prezzy Card will be mailed to you within 60 days of receiving the completed claim form. For multiple purchases on one receipt, each product must be claimed individually. Offer valid between 1st June 2016 and 31st August 2016.
Compare here:
https://en.wikipedia.org/w/index.php?title=Office_365§io…
$99 For Microsoft Office 365 Home Premium (5 computers)
https://www.heathcotes.co.nz/products/6gq-00017-microsoft-of…
$49.99 For 1
https://www.noelleeming.co.nz/shop/computers/computer-access…
Saw this yesterday, it was $59 before the sale started.