I will tune my guitar so that it's perfectly tuned (all the open strings (standard tuning-
E B G D A E))
I only recently noticed that if I move down the neck with the tuner plugged in, it gets more and more flat.

The A string for example, would be perfectly in tune while open, around the 5th fret or so it's a little flat (the 5th fret which should be a D is a little flat) and when you get to the 15th fret, it's almost a half step down! This can't be normal can it! I'm apply the same pressure with the fretting finger and plucking the string with the same force.

Being a Les Paul I'm confident it's not a problem with the quality of the guitar and I've taken perfect care of it since day 1.

Can anyone help me with this? Any help would be great- I just want to know what's up.

Thanks a lot
check your neck, whether its slightly bent or one of the frets don't seem to look right, you could try adjusting the action as well
like said, it's called intonation, and needs to be adjusted. this is true of all guitars.

how to do this, is explained in the first post of the set up thread.

you can click the green link in my sig to see it.

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Check your intonation. Its also important to know that a guitar wont have all frets perfectly in tune, thats just the way it is im afraid. Unless you get those crazy frets made to make all notes in perfect tune.
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well change your strings if they are older then 3 or 4 months...though that isnt a problem

The intonation is most likely the problem like everyone else has said. there are threads that explain how to fix it. But that might not be the whole problem, you might need to adjust the truss rod, or if its an extreme case (doubtful) you might need to move the entire bridge back or forward.

If you follow the instructions in a thread to fix your intonation and it works, thats great. If its still a problem, adjust the truss rod, fix your action. Do not adjust the truss rod unless you know what you are doing!! I adjusted the truss on my first guitar when I was playing for only a couple years, and I cracked my neck. Take it to a professional if you dont know how to fix it.
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