If you have a litter box by the front door, I would completely remove it or they will continue to use it! Cat's know what they like and where they like to do it...lolThere are no fewer than 6 litter boxes in acceptable locations and they have been using them for years. And one day they just form a liking for the front door. I wondered if they got scared of something in the basement (mouse?) but there is still the utility room and an upstairs bedroom they used to use (and still do a bit). It is all very puzzling.
