Deemed disclosure is a contractual provision treating all material in the data room (or some defined subset of it) as fairly disclosed against the warranties, regardless of whether each item is specifically referenced in the disclosure letter. Deemed disclosure clauses are seller-favourable and contentious in Australian practice; many buyers refuse to accept them, and where accepted they are typically narrowed to specific data room indices or specific categories of warranty.
The risk of broad deemed disclosure is that the seller can effectively neutralise warranty protection by uploading large volumes of unindexed material to the data room.