Thanks to Tightarse @ OZBargain for bringing up. I've tested and confirmed it works for Xbox One.
Originally posted @ hotukdeals
- Go to this website and click "Black Ops III Nuk3town support"
- Sign-up or login to Activision and ensure your account is linked to a gamertag (It will tell you if it isn't)
- Fill out the form with your details and select "My pre-order of the game didn't include a code"
- After submitting you should be taken to a new page with a reedemable code, redeem and enjoy!