An 80% attrition clause means you have promised the hotel that at least 80% of the rooms in your block will actually be booked and paid for. Block 100 rooms and 80 of them are your responsibility. If your attendees book 62, the hotel bills you for the other 18 — at the contracted rate, for every night the block covers, whether anyone sleeps in them or not.
The clause exists because the hotel gave something up to create your block. It held inventory off the open market and promised you a rate, and it priced both on your assurance that the rooms would fill. Attrition is the hotel handing the risk of your own forecast back to you.
How the bill is actually calculated
The common formula is simple: rooms short of the threshold, times the contracted nightly rate, times the nights held. Eighteen unfilled rooms below an 80% line, across two nights at a mid-range rate, is a five-figure invoice for beds nobody used. Some contracts soften this by charging lost profit instead of the full rate; some sharpen it by measuring attrition night by night instead of across the whole block. Which version you signed matters more than the percentage on the front page.
Three details that move the number more than the threshold
- The basis: damages on lost profit are dramatically cheaper than damages on the full room rate. Ask for lost profit before you sign.
- The measurement window: cumulative pickup across the whole block forgives a soft Sunday. Night-by-night measurement can trigger a bill even when the weekend sold out.
- The resell credit: if the hotel sells your unbooked rooms to someone else, a resell clause deducts them from your damages. It is a normal request, granted more often than it is offered.
The trap inside the pickup report
Rooms your attendees book outside the block usually do not count toward your threshold. The family that found the same hotel cheaper on a booking site, the group that took a rental instead — they travelled to your event and paid for lodging, and none of it reduces your attrition liability. Your block only sees the people who used your link, which is why organizers routinely owe attrition damages on weekends when the whole town was full.
In one event market we measured, roughly 70% of the lodging money moved inside the final 30 days before the event — long after the block was contracted and mostly outside it. The clause was written against a guess made months earlier; the demand showed up late and went wherever it liked.
What to do about it
Contract a smaller block than you expect to fill, and add rooms when pickup runs strong — adding is a phone call, unfilled rooms are an invoice. Negotiate the three details above. And give the late majority somewhere useful to land: an always-on lodging offer at your checkout captures the demand your block was never going to see.
A worked example, start to finish
Take a 100-room block, two nights, $180 a night, 80% clause. Your responsibility is 80 rooms. Suppose pickup lands at 63. The shortfall is 17 rooms, and the common formula bills 17 × 2 × $180 — $6,120, before tax, for rooms nobody used. Now rerun it with the two concessions this article recommends. On a lost-profit basis, hotels typically concede that an empty room saves them a share of costs, and the bill drops by a quarter or more. Add a resell credit and every one of those 17 rooms the hotel resold comes off the count entirely — on a busy event weekend, that is often most of them. Same block, same pickup, and the difference between the default contract and the negotiated one is thousands of dollars.
Run the same arithmetic on your own numbers before you sign anything: the block size, the threshold, the rate, and an honestly pessimistic pickup. If the worst-case number would hurt, the block is too big — not because demand is missing, but because the contract only counts a slice of it.
Questions to ask before you sign
- Is the damage basis full rate or lost profit? Get lost profit in writing.
- Is pickup measured across the whole block or night by night?
- Do resold rooms reduce my damages, and how is the resell documented?
- Can I reduce the block on a schedule as my real numbers arrive?
- Can I audit occupancy for my dates, and claim attendees who booked outside the code?