Perforations are totally optional. However, it is very beneficial because they allow for fast and easy separation of the two components of your ticket. One part is for you, to keep track of the attendance, and the other one for attendees to keep it as souvenirs. Sequential numbering is also optional. This is especially important to keep proper count of attendees. In fact, sequential numbering is mostly requested for proper management of financial reports. In short, perforations and sequential numbering are good for staying organized and managing your event.