Wedding Guest Etiquette 1. Responding Promptly When a wedding guest receives the invitation, he or she should respond promptly, Because the couple will be making many decisions based on the number of people who will be there On the other hand, if you must cancel after you have accepted, inform the couple as soon as possible. While it's considered very bad manners to respond after RSvP date, it's even worse to show up at the wedding after having not replied at all.Wedding Guest Etiquette 1. Responding Promptly When a wedding guest receives the invitation, he or she should respond promptly. Because the couple will be making many decisions based on the number of people who will be there. On the other hand, if you must cancel after you have accepted, inform the couple as soon as possible. While it’s considered very bad manners to respond after RSVP date, it’s even worse to show up at the wedding after having not replied at all