A hotel room block is a set of rooms an organizer reserves at a negotiated rate for attendees, released back to the hotel if they go unbooked by a cutoff date.
The organizer negotiates a rate and a number of rooms per night, the hotel holds them, and attendees book against the block with a link or a code. Unbooked rooms are released back to the hotel at a cutoff date, commonly three to four weeks out, after which attendees pay whatever the hotel is charging that day.
A block is rarely free. Most contracts carry an attrition clause making you pay for a share of rooms that go unbooked, so the block size is a forecast you are financially on the hook for. Blocking optimistically to look impressive to a hotel is the most expensive mistake in event housing.
They find a cheaper rate elsewhere, their corporate travel policy sends them somewhere else, or they never saw the link. Each one erodes pickup and pushes you toward attrition. The fixes are practical: put the booking step inside registration rather than in a follow-up email, and make the block rate genuinely competitive rather than nominally discounted.
Hotels, room types, rates and nightly inventory are set up inside the platform, and attendees book a room as part of registration rather than on a separate site. Events already running housing through Cvent Passkey can connect it instead, so the hotel booking happens straight after tickets are bought. See room block management software.