Tony and Ziva have never "officially" been together. They went undercover as married assasins in the episode "Under Covers" ep 3.08. In the episode "Shalom" ep 4.01, it was implied that there might have been something going on because it was mentioned to Ziva that while Gibbs had been on hiatus that Tony had been photographed going to her apartment frequently. in "Jet Lag" ep 7.13, it was implied that Tony and Ziva shared a bed while in Paris, but there was nothing saying that anything actually happened. Tiva shippers (myself included) often will read into certain scenes that something is going on between them or that something should be going on between them, but offically, nothing has happened that we know of.
