A banquet event order, or BEO, is the document a venue issues confirming every detail of a function, including timings, room setup, catering counts and charges.
Every operational detail of a single function: date, start and end time, room, setup style and layout, guest count, the full menu with dietary variants, bar arrangements, AV requirements, staffing, and the charges for all of it. A multi-day event generates one BEO per function, so a three-day conference with meals and receptions can run to a dozen of them.
The BEO is the document the venue's kitchen, banquet and AV teams actually work from. Anything agreed in a meeting but not written on the BEO will not happen. Once signed it also becomes the billing basis, which is why the guarantee number deserves more attention than anything else on the page.
The guarantee is the number of covers you commit to pay for, usually due three to five business days before the function. Venues typically prepare a small percentage above that, the overset, so a few extra arrivals are covered. Guarantee high and you pay for empty seats. Guarantee low and you are relying on the overset to absorb the gap.
Check the guest count, the service charge and tax treatment, the room setup diagram, and the timings against your own schedule. Setup style is the one that bites, because it gets copied from a previous event: a room specified as rounds when you need theater is a problem you discover at the worst possible moment.