This poly bag uncuffer and top sealer is designed for heat-sealing bags inside boxes after they are loaded or filled with products. The sealing machine uncuffs the bag from the carton top flaps, stretches the bag opening, applies a light vacuum to prevent ballooning, seals the bag, and then flattens it within the carton. This decuffer and sealer reduces labor and material costs, is simple to operate, and easy to adjust, thus promoting high efficiency and labor savings.