Punctuation tells the reader where to pause, what belongs together and what you mean. A letter with the right words and the wrong punctuation is misread; a letter with plain punctuation and no mistakes looks careful, which in a complaint, an application or a formal request is exactly the impression you want. These are the marks you need, with the rules that cause most errors first.
Full stop
Ends a statement. One space after it, not two. In British usage there is no full stop after Mr, Mrs, Ms, Dr or after abbreviations made of initials such as BBC and UK. Use short sentences and plenty of full stops; nothing improves a letter faster.
Comma
The comma separates. It has four main jobs:
- Items in a list: “I enclose the receipt, the warranty card and two photographs.” British usage does not put a comma before the final “and” unless it is needed for clarity.
- Two complete sentences joined by and, but or so: “I phoned on Monday, but nobody called back.”
- An introductory phrase: “After three weeks, the machine failed again.”
- Extra information that could be removed: “Your adviser, Ms Daley, logged the fault.” If the words between the commas are essential to the meaning, leave the commas out: “The adviser who answered logged the fault.”
The common mistake is the comma splice: two complete sentences joined by a comma alone. “I wrote on 2 March, I have had no reply.” Use a full stop, a semicolon or a joining word instead.
Apostrophe
Two uses, and only two.
- Possession: add ‘s to a singular noun (the customer’s order, James’s letter) and an apostrophe alone to a plural that already ends in s (the customers’ orders). Plurals that do not end in s take ‘s (the children’s school).
- Contraction: the apostrophe marks missing letters: don’t, can’t, I’m, it’s (it is), they’re (they are), you’re (you are).
Never use an apostrophe to make a plural: CDs, MPs, the 1990s, two photos. And its (belonging to it) has no apostrophe; confusing its and it’s is one of the most common punctuation errors in English. If you can replace it with “it is”, write it’s; if not, write its.
Colon
Points forward to what follows: a list, an explanation or a quotation. “Please send three things: the receipt, the warranty card and a photograph.” “There was one problem: the pool was closed.” Do not put a colon after a verb in a normal sentence (“I enclose: the receipt” is wrong).
Semicolon
Joins two complete sentences that are closely related, where a full stop would feel abrupt: “I reported the fault on 19 August; nothing was done.” It also separates items in a list when the items themselves contain commas. If you are unsure, a full stop is always correct instead.
Question mark and exclamation mark
A question mark ends a direct question (“When will the refund be paid?”) but not a reported one (“I asked when the refund would be paid.”). The exclamation mark has almost no place in a formal letter; one in a personal letter is plenty.
Quotation marks
Use them for words spoken or quoted exactly: Your adviser said “the refund will be with you in five days”. British publishers mostly use single quotation marks, with double for a quotation inside a quotation; either is acceptable in a letter as long as you are consistent. Put the full stop inside the closing mark only if the quotation is a complete sentence on its own.
Hyphen and dash
The hyphen joins words that act as one: a well-known brand, a 24-month contract, a two-page letter. It is not used after -ly adverbs (a highly regarded firm). The dash marks a break in a sentence or sets off an aside; in letters, commas or brackets usually do the job more quietly, and two dashes in one letter is enough.
Brackets
Round brackets hold an aside or a clarification: “the supplement (£140) was not refunded”. Square brackets show words you have added inside someone else’s text, as in the templates on this site. If a whole sentence is in brackets, the full stop goes inside; otherwise it goes outside.
Ellipsis and slash
Three dots mark words left out of a quotation. In a letter they otherwise suggest a thought trailing away, which is not the impression you want. The slash means “or” in forms (Mr/Ms, and/or); in running text, write “or”.
Lists in letters
A short list of items or requests is clearer as bullet points than as a long sentence. Introduce the list with a colon, start each item the same way (all nouns or all verbs), and punctuate consistently: either no mark at the end of each item, or a full stop after each one if the items are full sentences.
Three habits that fix most errors
- Prefer full stops to commas when in doubt. Short sentences are rarely wrong.
- Check every apostrophe: possession, contraction, or delete it.
- Read the letter aloud. Where you pause, there is usually a mark; where you do not, there usually is not.
Related guides
Spelling Rules in English, Writing Conventions, and the layout of greetings and sign-offs in Formal Letter Format.