There are some stand formats for professional business letter but before you go ahead and start on your own you should always check your company policies. There tends to be a company policy or a company preference for almost everything you might come across.
So, first – ask someone if there is a company preference.
If there isn’t see if you can find some samples of business letters that have been written by those that came before you. It should not be too difficult to find some business letter in the files as most companies will keep a copy of all correspondence that they send out.
Finally, if there is nothing to look back on the Block Format business letter is most widely accepted. Most businesses prefer this format because it is easiest to look at and it is clear where each section is.
The most recognizable feature of the Block Format letter is the fact that all paragraphs are justified to the left. There are no indents for paragraphs or for greetings or closings. Instead, they are identified and kept separate by a blank line.
The Block Format business letter will start with the return address of the company that is sending the letter. Sometimes this may be in the form of a letterhead that might be centered or right justified. Unless there is a letterhead though, you should keep it left justified.
Skip a line and put the date.
Skip a line and then move on to the address of the person/company you are sending the letter to. Make sure to include the name of the person the letter is addressed to, their position, the company name, and then the address.
Skip a line and put your greeting.
Skip a line and put your SUBJECT.
Skip a line and write your opening paragraph. This should be a short introduction that includes the purpose of the letter. It is usually only 2-3 sentences long.
Skip a line between each following paragraph.
Skip a line and put your closing and then skip 3-4 lines for a signature and then type your name (or the name of the person the letter is from) with your title.
If there are enclosures (additional documents they should take note of) skip a line and type ENCLOSURES. Put the number of enclosures in brackets if there is more than one.
If you are typing the letter for someone else go to the next line and type your initials in capital letters and if there is a typist (besides yourself) put their initials in lowercase letters.
Other types of business letter formats you might use include the Modified Block Format and the Semi-Block Format