advance reservation required
Used in notices, signs, or instructions to indicate that a prior booking is necessary. Often seen at restaurants, events, or services.
This restaurant requires advance reservations.
Participation in the event requires advance booking.
予約制 means a reservation system is in place, while 事前予約要 explicitly states that advance booking is required.
Compound of 事前 (beforehand), 予約 (reservation), and 要 (required).