Formal Letter Format: Block, Modified, Semi-Block

The three formats at a glance

• Full block. Every line starts at the left margin: date, addresses, salutation, paragraphs, close, and signature. Clean and simple, and the easiest to type.
• Modified block. The date, the closing, and your signature block start near the centre of the page; everything else stays left. It is the most common business layout because it looks balanced on the page.
• Semi-block. Like full block, but the first line of each paragraph is indented about five spaces. It is the least common today, seen mostly in traditional or older organizations.

If you are not sure, use modified block for business correspondence and full block when you want the simplest possible layout. Both are correct. Layout is only half of a company letter: what the law puts on the letterhead, who may sign, and the reference lines belong to business letter format on company paper.

Full block: everything left-aligned

Full block is the layout in the first template of the .docx above. Here is a complete example, a refund request, so you can see every part in place. It is one half of an exchange we run across two pages on purpose: the answer the retailer sent back is the worked sample on how to respond to a complaint, so you can read the same dispute from both desks.

Modified block: date and close move to the centre

Modified block keeps the body left-aligned but shifts the date, the closing, and your name to the centre of the page. That is the only change from full block. The skeleton looks like this.

Semi-block: indented paragraphs

Semi-block follows full block in every way except that the first line of each paragraph is indented about five spaces, the way a printed book indents. It looks more traditional and it is the least used of the three now. If a very formal or older organization expects it, keep everything left-aligned and indent only the start of each paragraph.

The parts of a formal letter

Whichever format you pick, the parts and their order are the same:

• Your address and the date. Write the date in full (15 September 2026), not abbreviated.
• The recipient's name, title, and address. Use the name where you have it.
• Salutation. "Dear Mr. Otieno:" with a colon in US business style, a comma in UK style. Close with "Yours sincerely" for a named person.
• Subject (RE:) line. One line in capitals telling the reader what the letter is about. It helps your letter reach the right desk.
• Body. State why you are writing in the first sentence, give the facts, and say what you want to happen.
• Close, signature, and enclosures. Sign above your typed name, and add an "Enclosures" line if you attach documents.

Email or a printed letter?

Email handles most business correspondence now, but a printed, signed letter still carries weight where a record matters: legal notices, formal complaints that may escalate, bank and immigration paperwork, and anything you may need to prove you sent. For those, print the letter, sign it, and keep a copy. For routine requests and confirmations, a well-formatted email using the same structure is fine. When you email a formal letter, put the RE: line in the subject and attach a signed PDF if a signature is expected.

Common mistakes

• "To Whom It May Concern." It reads as dated. Find a name, or use the person's role.
• Mismatched close. "Yours sincerely" for a named person, "Yours faithfully" if you did not name one.
• Abbreviated or wrongly ordered dates. Write the month in full to avoid confusion between US and other date orders.
• Confusing modified block with semi-block. Modified block moves the date and close to the centre; semi-block indents the paragraphs. They are not the same layout.

Sources

• Purdue OWL, basic business letters: block and modified block layouts and the parts of a letter. Semi-block is the older indented variant of the same structure, recorded in business-writing style guides rather than in a standard.
• Standard business-letter conventions for salutation punctuation, subject lines, and enclosures.