Event catering runs on different rules than daily service — quantities have to be estimated well in advance, and running short is far more damaging to reputation than a slightly conservative estimate. Asking the host for a guest count with some buffer built in avoids last-minute scrambling.
Transport and holding temperature for food between the kitchen and the event venue often gets overlooked until the food arrives lukewarm or overcooked from sitting in transit. Insulated containers and a realistic travel-time buffer protect the quality that was there when the food left the kitchen.
Clear communication with the host about menu changes, dietary restrictions, and final headcount — confirmed a day or two before the event, not just at the time of booking — prevents most of the disputes that come up after the event is over.