The postscript line in a business letter gets treated as a relic, something left over from the era of handwritten correspondence when adding a thought after signing was genuinely your only option. It isn't. A well-placed postscript can carry real weight in a formal letter, provided you understand what it's for and how to format it correctly.
What a postscript line is and what it does
A postscript is a line or short passage added after the signature block of a letter. The abbreviation "P.S." stands for the Latin post scriptum, meaning "written after." In printed business letters, the practical reason for the postscript disappeared long ago: word processors let you revise before printing. But the postscript survived because it does something structurally useful that revision cannot replicate.
Readers skim. Studies in direct mail and sales writing have consistently found that the P.S. is one of the most-read parts of any letter, second only to the opening line and the salutation. It sits at the end of the page, after the eye has already moved through the body, and it catches attention precisely because it's set apart. That makes it a smart place to restate your call to action, flag a deadline, or add one fact you want the reader to carry away.
It's not an error-correction device. If you've made a factual mistake in the body, fix the body. The postscript exists to add or emphasise, not to patch.
How to format the postscript correctly
Placement comes first. The P.S. sits below the signature block, below any listed enclosures, and below any copy notations. That sequence matters. If you've used an reference line at the top of the letter, the postscript echoes that document architecture: both are structural annotations sitting outside the main body.
The abbreviation itself can be styled three ways, and all three are acceptable in formal correspondence:
- P.S. (with full stops after each letter, most common in British and Australian English)
- PS (no punctuation, increasingly used in American English)
- PS: (with a colon, common in direct marketing)
Pick one style and use it consistently across all your letters. Don't mix P.S. in one letter with PS in the next. The abbreviation is followed by the text on the same line, with one space between the abbreviation and the opening word. No extra blank line between the abbreviation and the text.
A correctly formatted postscript looks like this:
P.S. The enclosed brochure includes the updated pricing schedule that takes effect on 1 November 2026. Please refer to page 4 before confirming your order.
Keep it short. One to three sentences is the norm. A postscript that runs to a paragraph is no longer a postscript; it's a second body section that belongs in the letter proper.
When to use a postscript in a business letter
Three situations genuinely call for one. First, reinforcing a deadline or a single key fact that the reader must not miss. If your letter offers a discount expiring on a specific date, restating that date in the P.S. ensures it lands even if the body text gets skimmed.
Second, adding a warm, personal note after a formal close. A letter negotiating contract terms might end with a professional close, then a P.S. that briefly references a conversation or mutual connection. This humanises correspondence that might otherwise feel transactional. Use this approach carefully: the tone of the P.S. should match the overall register of the letter.
Third, flagging enclosures or attachments that need specific action. If you've already cited your enclosures in the standard notation below the signature, the P.S. can direct the reader to a particular page or document. For guidance on citing enclosures correctly, see how to cite enclosures in business letters.
When not to use one
Avoid the postscript in internal memos and short status emails. It's a convention tied to formal letters, and it can read as affected in everyday correspondence.
Don't use it to apologise or to raise a new grievance. Apologies belong in the body, where they can be explained and contextualised. A P.S. apology looks like an afterthought, which is precisely the wrong impression when you need to rebuild trust.
Don't add a P.S. just because you've seen it in direct-mail templates. Some business writers copy the technique from sales letters without thinking about whether the letter's purpose supports it. A formal letter declining a proposal, for instance, rarely benefits from a postscript. The close should be clean and final.
P.S. vs P.P.S.: a note on sequencing
If you need to add a second afterthought after the first, the correct abbreviation is P.P.S., standing for post post scriptum. In practice, two postscripts in a single letter almost always signal that the body needed better organisation. If you find yourself reaching for P.P.S., revise the letter instead. One P.S. per letter is the working limit for formal business correspondence.
Putting it together
The postscript line follows the same logic as every other structural element in a formal letter: it has a defined position, a defined format, and a defined purpose. Treat it as a deliberate choice, not a throwaway addition.
A letter with a sharp P.S. draws the reader back to the one thing you most need them to remember. That's a useful tool. Format it correctly, keep it tight, and use it only when the content genuinely earns it.