I input as follows
go
x -1.000
y -1.000
z -1.000

And the Dro reads
x -0.9984
y -0.9970
z -0.9997
is there some way to correct for this?

Check for backlash and also make sure the steps per are accurate.
Movement is only as accurate as the components that mechanicaly drive it.
RICH

my components are not accurate by any means but i do not understand why if i tell the axis to move one inch the dro doesnt read one inch. I dont have encoders so im not sure why the difference?

Let me clarify. I do not have an external DRO on the machine I am talking about the computer screen readout in Mach 3. Hope this makes more sense.

That might just be the resolution of the axis's.
How coarse are the "Steps Per" settings in Motor Tuning ?

Russ

120 - 122 depending on axis. i am using some old ibm nema 23 motors with delrin ball screws that are pretty aggresive 1.75 inch per turn

I think you hit the nail on the head! I changed the resolution to 200 and got a lot closer consitantly. when my new motors and lead screws come in i suspect it will get much better!

Yes, that is quite coarse.
Setting a higher micro-step will help a bit, If your drives have that capability.

Then adjust your "steps per" accordingly of course.
Russ