As a general rule, write the invitation letters so that they can arrive at least two weeks before the event.
Normally keep these letters fairly short.
Consider writing the letter on decorative or festive stationery. For business events, company letterhead is also appropriate.
Handwrite your letters to add a nice, personal touch.
How to write a letter to extend an invitation to a social event:
Generally begin your letter with a warm, personal greeting.
Identify the event.
Indicate the purpose of the event.
Indicate the date, time, and location of the event and any other important information (such as a theme for the event, if there is one).
Include whether those attending should wear casual or formal attire, or any other special dress (such as costumes, uniforms, etc.).
If special guests will be attending, you may want to include this information in your letter.
If there is a cost for attending the event, include the amount.
If refreshments or a meal will be served at the event, include this information in the letter, as well. Also, if the event is a potluck or similar occasion, indicate the food or other item the person should bring.
If the host/guest of honor would prefer not to receive gifts, briefly mention this fact in your letter. Or if a particular type of gift is desired (as is the case for some bridal showers, for example), indicate the type of gift in your letter.
Include a request for readers to respond to the invitation by a specific date (RSVP), if desired.
Close by expressing your expectation that the event will be a success and your hope that the person to whom you are writing will be able to attend.
How to write a letter to accept an invitation to a social event:
As you begin your letter, express your appreciation for the invitation and thank the reader for inviting you.
Tell the person that you accept the invitation.
Include any other pertinent information, if necessary (for example, if you must arrive late or leave early and want to mention that fact).
Ask any questions you might have, or if desired, confirm details about the date, time, location, travel arrangements, or accommodations pertaining to the social event.
Let the reader know that you look forward to the event. Give your assurance that the event will be a success.
How to write a letter to decline an invitation to a social event:
Express your appreciation for being invited to the event.
If the event was to raise money or show support for a particular organization or group that you support, mention this fact to the reader.
Express your regret for being unable to attend the event.
Indicate why you cannot attend, if desired.
If appropriate, congratulate the person(s) (for a wedding, graduation, birthday, etc.). Or if the event was a fundraiser and you would still like to send a donation even though you cannot attend, state that you have included a contribution and indicate the amount of the donation you are making.
Express your hope that the event will be a success.