Well how often do you take your dog out? Did you know that one of the most important elements of leadership among dogs is that you walk with them for at least 45 minutes a day and does not include those short pee brakes? A dog starts marking if it's not properly trained or if there's a leadership to assume. If you don't, he has to. By the way, you need to remove the odor.
If males, neutering helps. But you must clean the area well so they can not still smell themselves in that spot. Get an ENZYME CLEANER at your pet store, and follow directions. Do it a few times to make sure .