When you include the acronym "RSVP" on a written invitation, you are politely requesting that the invitee respond to the invite with a "yes" or "no," often by a specified date. Yet, sometimes the recipient of the invitation fails to respond in a timely manner, which can leave you in a difficult position. Instead of waiting for a response that may never come, you can politely ask for the RSVP.
Wait until the last possible minute to receive a reply before calling the person. If you need the information to supply to a caterer, call right before you need to confirm the number of guests. Otherwise, you can call one or two days after the stated date for the RSVP.
Call the invitee and inquire if she received the invitation. Ask politely if she is planning to attend the invent by saying something such as, "I'm really looking forward to seeing you at the party, do you think you can make it?"
Ask her to call you by a certain date -- for instance, on Thursday if the event is on the following Saturday -- to let you know for sure if she can't give you a definite answer.
Follow up with a second phone call if she fails to call you and give you her response. Say something such as, "I'm calling to see if you are able to attend on Saturday. I'm hoping that you can make it."
As long as you are polite, don't hesitate to call any invitees and request a response. Sometimes people forget things and appreciate a reminder.
Don't email if you want a timely reply. If the person hasn't responded to your request for an RSVP, it's possible they will also delay in responding to an email.