In communicating about certainty, speakers make choices among available formulations and hearers will aim to recover speaker intentions. In two studies, we assess speakers' production choices and hearers' interpretations to test (a) how maximal certainty is formulated, (b) whether those formulations adjust depending on context, and (c) whether speakers' context-driven adjustments are apparent to hearers. We compare the lower-certainty formulation *I believe that the deadline is tomorrow* [believe] with two high-certainty formulations, *I know that the deadline is tomorrow* [know] and *The deadline is tomorrow* [bare assertion]. Given debates about which of the high-certainty formulations should convey higher epistemic standards, we investigate when (if ever) *know* is favoured, perhaps for its felicitous use in a wider range of contexts or perhaps for its strategic use in structuring subsequent dialogue via presupposition and accommodation. We investigated whether interlocutors align in the way they convey and recover meaning from statements about degrees of belief, comparing their behaviour across cooperative and uncooperative scenarios.