Response or reply cards are included with a wedding invitation to give you an accurate guest count for the reception. They are not used for ceremony-only invitations. The card and envelope are engraved or printed in the same style and paper stock as the invitation, but in a smaller size. Often they are included as part of an invitation set. It's a good idea to pre-address and stamp the reply envelope to make it as easy as possible for guests to RSVP via mail. If you prefer to receive replies via email or telephone, that's fine—just include the necessary information on the response card and skip the envelope.
It's also a good idea to include a "reply by" date, usually two to three weeks before the wedding. This gives hosts time to follow up with guests who have yet to reply and to give accurate head counts to wedding vendors, such as caterers.
_____ accept(s) [or, will attend]
_____ regret(s) [or, will not attend]
The favo(u)r of your reply is requested [or, Please reply] by July 26
The "M" precedes the space where the guest(s) write their name(s) and the name of their plus one, if they were invited to bring one:
M r. and Mrs. James Bailey
Or, for phoned or emailed replies:
The favo(u)r of your reply is requested [or, Please reply] by January 8, 2017
If you are offering an entrée choice at your reception, it's a good idea to include a way for guests to indicate their preference, usually by writing their name or initials next to their selection. Since guests may not remember which entree they chose, have a discreet system to alert servers, such as a decoration on the guest's place card, that indicates "beef," "fish," or "vegetarian."
James Filet Mignon
Monica Poached Salmon