Both hosts and guests may be confused about what RSVP means on an invitation. The term RSVP comes from the French expression "répondez s'il vous plaît", meaning "please respond." If RSVP is written on an invitation it means the invited guest must tell the host whether or not they plan to attend the party.
RSVP does not mean to respond only if you're coming, and it does not mean respond only if you're not coming (the expression "regrets only" is reserved for that instance).
It means the host needs a definite head count for the planned event and needs it by the date specified on the invitation. Most importantly, failing to RSVP does have its consequences.
Invitations requiring an RSVP will have instructions how to respond. Formal invitation, especially a wedding invitation, will have an enclosed response card that you can return in its provided envelope.
Informal invitations may have a telephone number, email address, texting address, or social media method to reply, with instructions. Be sure to respond in the way requested so the host doesn't have to compile responses from several different sources.
Electronic RSVP requests make it easy to respond by either email or links to a site with buttons to accept or decline. Hosts find this a convenient way to monitor responses and nothing should get lost in the mail.
If the RSVP says, "regrets only," you only respond if you are unable to attend.
If you don't respond, the host will expect you to be there. Be sure to use the requested method to respond if you can't attend. It's best not to respond if you will attend, as a response may be confusing to the host. Use other methods to express your enthusiasm about attending the event.
No RSVP Requested
If you check the invitation and there is no request for an RSVP, you have no obligation to respond.
But it is still best to contact the host to tell him you are coming, especially if you want to bring a guest. It could be they simply forgot to include the RSVP request. However, once you say you are coming, you should treat it like a full obligation, just as when an RSVP is requested.
The RSVP should make it clear who is invited. Couples are often named together, sometimes followed by "and family," which would include your minor children. It may indicate you are able to bring a guest, often called a "+1." If you don't see any indication that the invitation allows you to bring a guest, you should assume it is only for you and anyone else explicitly named.
There may be a blank to write in a number of guests. Check further on the invitation to see what the limits are for a number of guests. If you are considering more than one or two, contact the host to ensure the event can handle the number you are proposing to bring.
If you can't leave behind house guests or others, decline the invitation. You can tell your host the reason you are declining, preferably without fishing for an expanded invitation. If the host is able to expand the event, he may offer an invitation that includes them.
RSVP requests often include a deadline for response. This is an important deadline as the host is finalizing numbers for the caterer, event site, favors, etc. It's best to respond as soon as possible rather than delaying. The host then may be able to offer invitations to other people who didn't make the first cut for invitations, or accommodates extra guests of other invitees.
If you want to attend but you have difficulty giving a definite response before the deadline, it's best to decline. It's best to be honest with the host about your situation. The only way they can help make accommodations for you is if they know you need them. You can contact the host with your regrets and explain what is keeping you from being able to know you can attend. Ask if there is any flexibility but understand if there isn't.
The earlier you make this call, the better, rather than waiting until the host has followed up with requests to return the outstanding RSVPs.
Canceling or Changing an RSVP
It is bad form to cancel an RSVP unless you have a very good reason, limited in general to illness or a death in your family. The host will already have made plans based on your attendance. For any other reason, you may expect that the host will not invite you to future events.
The time to decline is when you make the RSVP, considering all the factors as to your scheduling, finances, and other opportunities. If you declined the RSVP but discover you can attend the event, contact the host to see if it is possible. Be sure to express that you understand that it probably isn't possible as your host may have to tell you it is too late. Make that easy on the host if you want future invitations.
Why It's Inconsiderate Not to RSVP
Many people don't RSVP because they don't want to disappoint the host. This attempt to spare their feelings usually causes more trouble than a simple no. An incomplete list of respondents can cause numerous problems for a host, including difficulty in planning food quantities, issues relating to minimum guarantees with catering halls, uncertainty over the number of party favors, and difficulties in planning appropriate seating, among other things.
Sometimes people don't send a RSVP by the requested time because they are unsure if they will be able to attend and don't want to commit to an answer. If this is your situation, it's best to be honest with the host about your situation. The only way they can help make accommodations for you is if they know you need them.
The Bottom Line
The next time you see RSVP on an invitation you receive, please call, write, or text your host and respond promptly. Your host will be eternally grateful and you are more likely to be invited again in the future.