What should I do if I notice my toilet leaking under the tank?

If you notice your toilet leaking under the tank, you should first turn off the water supply to the toilet to prevent further damage. Then, inspect the tank and surrounding areas for any visible cracks or loose connections. If you are comfortable doing so, you can try tightening any loose connections or replacing any damaged parts. If the issue persists, it is best to contact a professional plumber to assess and repair the leak.