The postscript has survived the move from handwritten letters to typed memos to email, and it still trips writers up. How to format p.s. is a surprisingly contested question: should the letters be uppercase or lowercase? Do you need periods? Does a colon follow? The answers are simpler than the debate suggests, and getting this detail right says something about how carefully you write.
P.S., p.s., or PS: which form is correct?
All three appear in published writing. The most widely accepted form in formal business correspondence is P.S., with capital letters and periods after each one. This follows the standard abbreviation convention for Latin phrases (postscriptum, meaning "written after"). The Chicago Manual of Style treats abbreviations like this with periods, and most major style guides lean toward P.S. as the default.
Lowercase p.s. is also correct and appears frequently in informal correspondence. It looks slightly more casual, which can work in personal emails but feels out of place on formal business letters or press releases.
PS (no periods) is common in digital contexts. Email culture has stripped the periods from many abbreviations, and PS follows that pattern. It reads fine in a marketing email or an internal Slack message. In a formal letter, drop that habit and put the periods back in.
Does a colon go after P.S.?
This is where writers hesitate most. Both forms work:
- P.S. The meeting has moved to Friday.
- P.S.: The meeting has moved to Friday.
The version without a colon is more common in American English. The version with a colon is more common in British English and some European business traditions. Pick one and be consistent across your document or organization's style. Don't agonize over it. The reader isn't going to notice either way, but inconsistency within a single piece of correspondence does look sloppy.
Where does P.S. go on the page?
Placement is not optional. P.S. goes after your closing line and signature, never before. In a letter, the sequence is: body text, closing (e.g., "Sincerely,"), your name and title, and then P.S. on a new line below that. Some writers add a blank line between the signature and the P.S. That's fine. What's not fine is dropping the P.S. before the signature, which defeats the purpose entirely.
In email, the same rule applies. Write your sign-off and name, then add P.S. beneath. Many email clients auto-format a signature block; put your P.S. above the automated signature, not below it, or it'll be visually buried and likely ignored.
Can you write a P.P.S.?
Yes. P.P.S. (post-postscriptum) is legitimate when you genuinely have a second afterthought. It goes below the P.S. In practice, if you find yourself writing P.P.S. regularly, the real problem is that your letters need better organization before you hit send. One postscript is a flourish. Two is a sign the main body needs reworking.
When to use P.S. in business writing
The postscript earned its place in the era of handwritten letters, where adding to the main body after signing was physically inconvenient. That constraint doesn't exist anymore. So why use P.S. at all?
Two reasons remain valid. First, emphasis. Research on direct mail and marketing emails consistently finds that readers often skip to the P.S. after reading the opening line. A P.S. that restates your core call to action reaches readers who skimmed the middle. Second, warmth. A personal postscript note in a business letter (a congratulation, a friendly aside, a reference to a shared conversation) can add a human touch that a formal body paragraph can't.
What P.S. isn't for: burying essential information the reader needs to act on, correcting a mistake in the main text (use a proper correction or a follow-up message instead), or padding out a thin letter. Just as knowing when to use "thank you in advance" matters as much as how to write it, the same applies here. P.S. works when it's genuinely an afterthought or a strategic emphasis, not a lazy catch-all.
Quick formatting reference
To put it plainly: use P.S. in formal correspondence and PS or p.s. in informal digital writing. Follow it with a space (not a tab, not a colon unless your style calls for one). Write one sentence or two at most. Place it after your signature. Keep the content either strategic or personal, never filler.
The same attention you give to formatting conventions like AM and PM should extend to the details that appear at the very end of your correspondence. Readers notice when those final lines look polished, even if they can't always say why.