Check your messages
As an apology for some of the issues with the Halo: The Master Chief Collection, Microsoft announced that it was gifting players a free month of Xbox Live. That free month is happening right now, and a message should be in your Live inbox now indicating that it has been applied.
To earn it, all you had to do is play the game before December 19, 2014. In addition to this bonus, you’ll also get a free ODSTadd-on, as well as a free remastered Halo 2map later this year.