What should formal letter header contain?

It is a custom that formal letter header consists of your address and the date. Your name should not be included in this part. In traditional formal letter form it is not acceptable to include Telephone numbers and email addresses within header of the letter. However nowadays, it is quite acceptable to include phone numbers, e-mail address and website. In some countries, people tend to include here basic company data as well, such as tax numbers, registration numbers, website address, and similar.

Following traditional form of the formal letter, and using a block format, the header goes in the top left-hand corner of the page, and it should look like this

97 5th Ave.
New Your, NY KSR 3S7
December 19, 2015

If you would like to place your email address and phone number it can look like this:

97 5th Ave.
New Your, NY KSR 3S7
December 19, 2015

(800) 5454 999

namesurname@site.com