HELP! My 1yr old min pin will no stop "marking" in the house how can i fix this?

I have a loving, friendly, active 1 yr old male min pin. Hes such a good dog and absolutely brilliant sometimes a little too smart. He knows where to go when he needs to be let out and will go to the door and if you dont see him right away he will come get you and let you know he has to go which is beautiful and listens to ques such as " gotta go potty " and goes. Only problem is he will go outside then come back indoors and pee on something not a lot of pee but a decent sprinkle on things like my mothers jacket, certain doors, the garbage can and things that smell different. I have definitely clified this as marking, he did have a bathroom issue when he was a puppy but has not peed on any carpets or rooms or anything since and only marks now and i have no idea what to do as he is ruining thousands of dollars worth of things. Someone have any idea other than being fixed [ hes going to get fixed as soon as he turns 1 ]