The best urine stain remover for hardwood floors is hydrogen peroxide. You can buy it at a drugstore or in the drug section of a supermarket. Fill a squirt bottle with the solution. Do not dilute. the drug store. (The solution is about 3.5% out of the bottle). Squirt the stain and let it sit for about 1 minute. Now you will be able to scrape off the varnish. Apply the solution again liberally. Let it react (it will foam a lot)for at least 2 hours. You may have to sand the spot and reapply the peroxide several times. You should then refinish the spot. But it does work!