If your toilet is leaking under the bowl, inspect the base of the toilet bowl for cracks or other damages. If no damages are found (cracks, chips or burrs), then the wax ring may need to be replaced. Pay close attention to the wax ring when you pull the toilet; if the wax ring appears more corroded on one side than the other, the toilet may be sitting on an unlevel surface. This will cause the wax ring to erode unevenly and cause leaks. All toilets must be installed on a level surface, front to back and side to side.