Hi, I have had my HTC M8 for nearly a year when it started to not charge fully. Even if I left charging overnight it would only charge to about 75%.
After doing a factory reset to try and solve the problem, I returned to Orange under insurance, and, received another phone.
This is doing exactly the same!
The problem seems to be pointing at my charger (which is genuine HTC). Would a charger be able to cut out at a certain point in charging, or, does anyone have any other ideas.
Thank you

Have you tried topping it up by plugging it into the usb socket of a laptop / pc. etc to rule out the wall charger.

The harder may not be giving a full output at 5v which may result in charging aborting prematurely. As Kenny says, try charging from the computer or find another mini USB charger. As long as it outputs 5v it should work ok.