What is the proper etiquette of plus-ones? I know when it comes to a married or engaged couple you invited them both, no question, but what about friends who are single? We were planning on giving plus-ones to friends that we know are in serious relationships, but what about everyone else? The friends we are inviting all know each other, so I figure this shouldn't be an issue. Our budget/ venue can't accommodate a date for EVERYONE and I don't want to have to cut anyone from the list, but I'd like to know the general rules.