You can remove the toilet and shim it if the lean is not too great, but make sure you replace the wax ring with one that is thick enough to make up any difference in height from side to side.

: I just had my basement finished with a new toilet and sink added. During the process the contractor jackhammered the floor to put in the plumbing for the toilet and then re-cemented the floor and used leveller to smooth it out. Vinyl was put over this. After the plumber left yesterday I noticed that the toilet leans to the right. It's more obvious when you sit. I'm assuming the contractor did not actually get the floor level where the toilet sits. What can be done about this? Can it be shimmed now? Does the whole floor have to be fixed? That seems almost impossible at this point.