Vega IV

Human historians in the post-Time War universe, following the Siege of Trenzalore, acknowledged Vega IV as a world which had fallen to the expanding Dalek Empire. (PROSE: Dalek: The Astounding Untold History of the Greatest Enemies of the Universe) Indeed, the Daleks had conquered the Vega System during the invasion of Mutter's Spiral and the Second Great Dalek Occupation. (AUDIO: Invasion of the Daleks)

Behind the scenes
As mentioned in Dalek Empire: The Scripts, Vega VI was originally called Vega IV before Clayton Hickman said that it sounded like "vague guffaw".