Solved AMD, Windows 8.1 and 4K television.

My son has his PC connected to a Sony Bravia 4K television, he's installed the latest Catalyst drivers, and after the restart Windows 8.1 won't allow him to change the screen resolution to the 4K settings, it's got him stuck at 1920x1080. He also has the PC connected to the TV via HDMI (don't know if that's the issue), any help getting Windows 8.1 to allow the 4K resolution settings is greatly appreciated.

You need to find out what resolutions the AMD video card will take. If I recall, 4K is 3840 x 2160 -- and it could be that the card will not support resolutions that high.

I had a real good look at it late yesterday while he was out, and he had upscaling checked, as soon as I unchecked the upscaling box he could get resolutions up 4096x2160 so all is good. He apparently has upscaling checked when he watches movies, but it seems to interfere with higher resolutions while playing any sort of game.