REGISTERING FOR GIFTS
One of the trickiest areas of elopement etiquette is whether or not to register for gifts after the fact. If you are planning a post-elopement reception, the answer is yes. Gift registries are meant to benefit guests, allowing them to select items with confidence instead of casting about for ideas and worrying you'll have to return what they give you. It is imperative, however, that no mention of gifts or registries is included on the invitation to the reception (this is true of all parties except for showers). If you are asked directly what you would like, the correct response is something along the lines of, "Anything that you choose for us is going to be wonderful and much appreciated, but we did register for some gift options at X in case any of our guests wanted ideas." If your parents are being asked the same question, they can give a similar response.
It's important to note that it is equally impolite to indicate on an invitation that you don't want gifts – any mention of gifts is an invitation faux pas (again, with the exception of shower invitations which are gift-specific events). If you are adamant you don't want or need gifts, the best thing to do is create a registry that will benefit a charitable organization – your guests can make donations in your name, and a worthy cause will benefit. If you opt not to have a post-elopement reception or gathering, registering is unnecessary, as marriage announcements do not carry the obligation of a gift.