[UPDATE] Following the publication of this story, all Xbox One live services returned to normal operation.
The original story is below.
Using prepaid cards or codes for downloadable items or Xbox Live subscriptions is one of the affected services for the UK. However, GameSpot was able to redeem a 12-month Xbox Live code today from our office in London.
What's more, joining other Xbox Live members in online games and posting game performance or viewing the performance of other member is also currently unavailable for some in the US and UK.
In addition, Microsoft acknowledged that players in the US and UK are experiencing issues joining the Squad Assault game mode for Call of Duty: Ghosts. Microsoft said it is "hard at work" with Activision to bring this service back online.
It is not clear how many are affected by the Xbox Live issues today are or when the services are expected to return to normal operation. A Microsoft representative was not immediately available to comment.