<cite>Rao and Tetreault (2018)</cite> used independent neural machine translation models for each formality transfer direction (informal→formal and formal→informal). Inspired by the bi-directional NMT for low-resource languages , we propose a unified model that can handle either direction -we concatenate the parallel data from the two directions of formality transfer and attach a tag to the beginning of each source sentence denoting the desired target formality level i.e. <F> for transferring to formal and <I> for transferring to informal.