Date (Write down the date on which this letter is being sent)
Name (Mention the name of the recipient)
Designation (Mention his designation, if applicable)
Company (Mention the name of the company to which he/ she belongs, if applicable)
Address (Mention the complete address of the recipient or the address of the company he belongs to, whichever is applicable)
Respected Sir/Ma’am (You may even write Mr. /Ms. /Mrs. Last Name)
Subject: Write down the purpose of writing the letter in one line
First Paragraph: Ask sorry for the mistake occurred. State the reason for such a mistake.
Second Paragraph: Tell the recipient as to how much you value his/ her association.
Third Paragraph: Apologize once again and tell him / her that such mistake would not be repeated in future.
Thanks and Regards,
Name (Mention the name of the person writing the letter)
Designation (Mention the designation of the person writing the letter, if applicable)
Name of the Organization (if applicable)