Birthdays are occasions to celebrate with friends. However, it is important to make your friends aware of your upcoming birthday so that they can mark the day on their calendars. Sending a letter to a friend to invite him to your birthday celebration is a thoughtful way to let him know that his presence at your celebration would be meaningful to you. To avoid your friend not being able to celebrate with you due to a scheduling conflict, send the invitation letter for enough advance notice about your birthday.
Decide whether you will handwrite the letter or type it on your computer. If you are handwriting the letter, select stationary or paper on which to compose the letter. If you are writing the letter on your computer, have printer paper on which to print the letter or your friend's e-mail address to which you can send the letter.
Begin the letter by writing the date and your friend's name. You can precede the friend's name with "Dear" or "Hi." Either way, a personal, direct address to your friend with his or her name should appear before the body of the letter.
Compose the body of the letter. It can be anywhere from several sentences to several pages worth of text. The letter might be a brief invitation to your birthday celebration or it might be a letter that discusses current events in your life and how much the friend means to you. Include the date and time of your upcoming birthday celebration in the letter and what has been planned for the celebration, if anything. Additionally, let your friend know how old you will be turning on your birthday. If there is a specific dress code or theme to your celebration, put this in the letter.
Sign the letter. Your signature should be legible so your friend knows who sent the letter.
Send the letter to the recipient via the United States mail, personal delivery, fax or e-mail.
If you do not hear a response from your friend after a reasonable amount of time has passed since sending the letter, contact your friend to see if he received the invitation.