The date line sits near the top of every business letter, and most writers give it almost no thought. They type a date, move on, and assume the rest takes care of itself. It doesn't. The date line follows specific conventions that vary by country, audience, and style guide, and a misformatted date can quietly undermine the polish of an otherwise professional document.
Where the date line goes
In a proper business letter format, the date appears after the sender's address and before the inside address (the recipient's details). In a block-style letter, every element sits flush to the left margin. In a modified-block or semi-block style, the date line aligns with the centre of the page or to the right margin, depending on the variant.
One line of blank space sits above the date, and two lines of blank space follow it before the inside address begins. Don't compress these gaps. White space is structural here, not decoration.
How to write the date itself
This is where errors multiply. Three formats compete in professional correspondence, and they aren't interchangeable.
- American format: Month Day, Year — for example, August 28, 2026.
- British and Australian format: Day Month Year — for example, 28 August 2026.
- ISO 8601: Year-Month-Day — for example, 2026-08-28. This format suits technical, international, or government documents.
Write the month in full. "Aug." is fine in a diary. In a business letter, abbreviating the month reads as careless. "August" costs two extra characters and reads as deliberate.
Ordinal suffixes — 28th, 1st, 3rd — are a relic of older correspondence styles. Drop them. "August 28, 2026" is correct. "August 28th, 2026" is technically acceptable but reads as informal. Most contemporary style guides, including the Chicago Manual of Style, recommend the plain cardinal form.
The comma question
American format requires a comma between the day and the year: August 28, 2026. When a full date appears mid-sentence, a second comma follows the year: "The letter dated August 28, 2026, confirmed the agreement." Both commas are required. The second one trips up a surprising number of writers.
British format (28 August 2026) uses no comma at all. Adding one is an Americanism and looks wrong to British and Australian readers. If you're writing for a global team, pick the format that matches your primary audience and stick to it throughout the document.
What not to include in the date line
The day of the week doesn't belong here. "Thursday, August 28, 2026" looks overly detailed in a formal letter. If the day matters (for a meeting notice, for example), mention it in the body of the letter.
Numeric-only formats create ambiguity. "08/28/26" means August 28 in the United States. In the United Kingdom it is read as the 8th of the 28th — which is impossible, flagging the confusion rather than resolving it. "28/08/26" inverts that problem for American readers. Spell the month out and the ambiguity disappears entirely.
Don't use two-digit years. "2026" is unambiguous. "26" is not.
Matching the date line to your letter's style
The date line isn't isolated from the rest of the document. Its format should be consistent with how dates appear in the body of the letter. If you write "28 August 2026" at the top, don't write "8/28/2026" in the text below. Consistency is what separates a polished letter from one that was assembled in a hurry.
If you're writing for a client based in a different country from your own, adopt their date convention. It signals awareness. A British client receiving "August 28, 2026" from an American firm won't be confused, but a British client receiving "28/08/26" from that same firm might wonder whether the sender knows who they're writing to.
For correspondence that needs to match formal house style, check your organisation's style guide or, if none exists, choose the APA Style or Chicago convention that fits your audience and note it as a standard for future documents. Consistency across letters builds credibility. Inconsistency chips away at it.
A practical checklist
Before you send any formal business letter, run through these five points on the date line specifically:
- Is the month spelled out in full?
- Does the format match the audience's convention (American, British, or ISO)?
- Is the year written in four digits?
- In American format, is the comma after the day present?
- Does the date format match how dates appear in the body text?
Five seconds of checking. The date line is the first content your reader sees after your address. Getting it right costs almost nothing. Getting it wrong signals that the details matter less to you than they should.