Apologies if this has already been posted, didn't find when I searched.
Both Amazon Video and Google Play are offering a 50% discount on any one season. However, as per the picture attached, it also works for box sets. I already purchased GoT-S6 and Suits S6 at 50%.
Amazon Video discount code: 50SEASONS
Google Play discount code: Locate the offer from scrolling offers at the top, select and click redeem before going for purchase. 50% applied at the time of checkout.
EDIT: Google Play code SEPTTV50 (thanks raj75)
Wide variety of individual seasons and box sets to choose from. Also on Google Play, works in addition to ongoing discount on TV seasons.