Below are the rules that you should bear in mind when writing formal letters:
Do not use informal language such as using contractions when making formal letters. In addition, formal letters should be simple and short. They are not intended to bore the reader, as formal letters are usually important.
When writing the return address, it should be at the top right hand corner of the paper while the inside address is written below the return address but at the left corner of the page.
It is important not to abbreviate the month when writing dates. You can place the date either at the left or right part of the paper.
It is best to research the name of the recipient but if there is no way that you can do this, a salutation that says, “Dear Sir or Madam" is always safe. If you have a name, always address him/her with their title.
Always make sure to use formal closing phrases such as “yours sincerely" when ending a formal letter.