Many corgis can jump

Though it's very important that they not be overweight and they should be x-rayed to make sure their shoulders and hips are ok.

You should wait until a corgi is at least a year or year and a half before jumping what they would normally jump (usually 8" or 12").  Some puppies are taught on little tiny jumps or poles on the ground, but get a vet's ok before doing so.  It's best to wait till their growth plates have closed.  The way to tell if they're closed is by an X-ray.