In this paper, we distinguish between plan-based Denial of Expectation (DofE) signalled by “but”, which occurs in task-oriented (TOD) only, and the more commonly researched expectation-based case in TOD and non-task-oriented dialogue (NTOD). We present an algorithm for DofE which addresses plan-based “but” cases in TOD.We address how indirect Speech Acts (SAs) need to be resolved in order to address many of these cases and present a mechanism to do so in TOD within the IS framework. We then argue that this treatment of DofE can be extended to address generation of plan-based DofE in monologue with very few modifications.