As we mentioned before, a cat marks with urine. This type of behaviour is common in territorial, whole males, in females in heat, and sometimes (in rare occasions) in castrated males. If it is a whole male, the best thing is to castrate it soon before it changes from a hormonal problem to a dominance problem. Just the same, if it is a female in heat, a ovariohysterectomy (or neutering) is highly recommended as soon as possible.
If, on the other hand, it is the case of a castrated male or an adult animal which hadn't presented such behaviour previously, we need to look for the cause. These cases are usually triggered by anxiety or stress. We need to search and examine what caused this sudden change in its behaviour: moving to a new home, a new animal shares the house, remodeling, long absences from its owner(s),... Whenever this case happens, it needs treatment to help it overcome this period of fear and insecurity.