Jamie Topliffe was last seen in the Chester Road area of the town at 1.30pm on Monday 1 July 2024.
He is described as white, six feet one inches tall and wearing a grey tracksuit with a long black puffy coat. He was also wearing grey Nike trainers and a cap.
He may have travelled to Essex and maybe with 16-year-old Dylan Young who has also been reported missing.
Anyone who sees Jamie (or Dylan) should call Kent Police on 999 quoting reference 01-1708.