Punctuation for IELTS Writing: commas, full stops and apostrophes
Quick answer
Punctuation is marked inside Grammatical Range and Accuracy, not as a separate criterion. The public descriptors move from commas and full stops that are often wrong or missing, to punctuation steady enough that a reader stops noticing it. In practice, end each complete idea with a full stop, never join two full sentences with only a comma, and put a comma only where it has a job: after an opening phrase, around extra information, in a list, and before "but" or "so".
IELTS Mentor AI marks Speaking and Writing answers on the four criteria, Grammatical Range and Accuracy among them, and explains each mistake it finds.
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Punctuation is the part of grammar a candidate can fix fastest. It has few rules, and a short check at the end of the test catches most errors. This guide covers the full stop and the comma splice, what each comma does, where a comma does not go, and the smaller points about apostrophes, capitals and Task 1 numbers. For the whole criterion, start with the pillar guide to IELTS grammar.
Key takeaways
- Punctuation is marked inside Grammatical Range and Accuracy. It is not a separate criterion.
- Two complete sentences need a full stop between them, not a comma alone. That error is called a comma splice.
- Give every comma a job: after an opening phrase, around extra information, in a list, before “but” or “so”, and after a linker that starts a sentence.
- No comma goes between a subject and its verb, before “that”, or around a defining clause.
- A full stop is never wrong, so semicolons and colons are optional.
- IELTS publishes no list of punctuation rules and no count of errors per band.
Where punctuation is marked
The public Writing band descriptors place punctuation inside Grammatical Range and Accuracy, which IELTS.org weights equally with the other three Writing criteria. Spelling sits inside Lexical Resource. Neither is a criterion of its own, and neither is ignored.
The site’s paraphrases of the descriptors, in the Writing band descriptors explorer, show how the wording moves:
- At band 4, commas and full stops are often in the wrong place or missing.
- At band 5, punctuation is unreliable, and together with frequent grammar mistakes it makes a reader work.
- At band 6, there are punctuation mistakes, but they rarely get in the way of the meaning.
- At band 7, grammar and punctuation are both under good control, and a few errors remain.
The step from band 5 to band 6 is described as punctuation becoming steady enough to be ignored. The aim is therefore not clever punctuation. It is punctuation a reader never has to think about.
IELTS publishes no list of punctuation rules, no count of errors allowed at any band, and no penalty for a single mark. Nothing here promises a band.
The full stop and the run-on sentence
Every complete idea ends in a full stop. The lowest-band error is full stops that are missing, and the site’s band 4 traps list joining every idea with a comma and no full stop. The error that survives much longer is the comma splice, which joins two complete sentences with only a comma.
- Splice: “The number rose, it then fell.”
- Fixed with a full stop: “The number rose. It then fell.”
- Fixed with a joining word: “The number rose, and it then fell.”
- Fixed by dropping the second subject: “The number rose and then fell.”
A splice is easy to miss because it looks like a natural pause. The site’s band 6 traps list comma splices that survive every check for that reason. The test: if both sides of the comma could stand alone as sentences, and only the comma joins them, it is a splice.
A linker does not repair a splice. “The number rose, however it fell” is still a splice, because “however” is not a joining word like “but”. Write “The number rose. However, it fell.” or “The number rose, but it fell.”
A run-on sentence is the same fault with no comma: “The number rose it then fell.” Fix it the same way.
Commas by job
Use a comma when it does one of these five jobs, and not otherwise.
After an opening clause or phrase
When a sentence starts with something other than its subject, a comma usually marks where the main clause begins.
- “Although unemployment rose, spending stayed steady.”
- “In recent years, more people have moved to cities.”
- “To reduce traffic, councils can limit parking.”
A very short opening phrase may go without one, but the safe habit is to include it.
Around non-defining relative clauses
A clause that adds extra information about a noun that is already clear sits between two commas: “The museum, which opened in 1990, attracts many visitors.” The guide to relative clauses for IELTS Writing and Speaking covers the full rule, including why “that” is never used after a comma.
In lists
Separate three or more items with commas, and put “and” before the last one: “Housing, transport and food rose.” A comma before “and” in a list is optional in British writing. Choose one style and keep it throughout the script.
Before “but” and “so” joining two clauses
When “but” or “so” joins two complete clauses, put a comma before it: “Wages rose, but living standards did not.” “Housing is scarce, so many students share flats.” When the second part has no subject of its own, it is not a clause, and no comma is needed: “The line rose and then fell.” “Wages rose but did not last.”
After a linker at the start of a sentence
A linker that begins a sentence takes a comma after it: “However, exports fell.” “For example, buses are cheaper.” “In addition, cycling lanes improve safety.” In the middle of a sentence, the same linker is set off by two commas: “Exports, however, fell.” The guide to linking words and coherence covers which linkers to use.
Where a comma does not go
Over-punctuation is as visible as under-punctuation. Three places never take a comma:
Between a subject and its verb. Wrong: “The number of visitors to the museum, rose.” Right: “The number of visitors to the museum rose.”
Before “that”. Wrong: “Many people argue, that taxes should rise.” Right: “Many people argue that taxes should rise.”
Around a defining clause. A clause that tells the reader which noun you mean has no commas. “Students who work part-time earn less” means only those students. “Students, who work part-time, earn less” says all students do. The commas change the meaning.
Semicolons and colons
Both are optional, and a full stop is never wrong. A semicolon joins two complete sentences that are closely related: “Public transport is quick; private cars are not.” A colon introduces an explanation or a list: “There is one clear cause: delay.” If you are unsure of the rule, use a full stop instead. IELTS publishes no requirement to use either.
Apostrophes
“Its” and “it’s“. “Its” shows possession and has no apostrophe: “The city and its suburbs”. “It’s” is a short form of “it is” or “it has”, so it does not belong in a formal essay at all.
One owner and many owners. Write the apostrophe before the “s” for one owner and after it for several: “the country’s economy” is one country, “the countries’ economies” is more than one. Irregular plurals add the apostrophe and “s”: “people’s habits”, “children’s schools”.
No apostrophe in a plural. Write “the 1990s”, “three graphs” and “many studies”. Writing “1990’s” or “graph’s” for a plural is a frequent slip.
Capital letters
Countries, nationalities, languages, months and days take capitals: “Brazil”, “Brazilian”, “English”, “March”. Seasons and school subjects take lower case: “in summer”, “physics”, “economics”. A subject that is a language keeps its capital: “English”, “French”. General words such as “the government” and “the city” stay in lower case unless part of a name.
Task 1 specifics
Task 1 is full of numbers, and each kind has a habit.
- A year or period opening a sentence is followed by a comma: “In 2010, sales fell.”
- A decade has no apostrophe: “the 1990s”.
- Thousands take a comma, as in 1,200, and decimals take a point, as in 3.5.
- Choose “20%” or “20 per cent” and keep to it.
- A list of three categories takes commas and “and”: “Housing, transport and food”.
- A range takes “from” and “to” with no comma: “from 20% to 35%”.
For what to describe in the first place, see the guide to Task 1 charts, graphs and tables.
Contractions
Write “do not”, “it is” and “cannot” in full in an essay. This is a register point and not a punctuation rule: contractions belong to speech and informal letters, and an essay is written in a more formal voice. It is advice, not a published requirement, and it also removes the “its” slip above.
Checking your script
In the last minutes, check punctuation on purpose. Read each sentence slowly and look for these in order:
- Does every sentence end with a full stop, and does the next one start with a capital?
- Is there any comma with a complete sentence on both sides? If so, add a full stop or a joining word.
- Is there a comma between a subject and its verb, or before “that”? Delete it.
- Does every opening phrase and every sentence-initial linker have its comma?
- Does every apostrophe belong, and is there one in a plural that should not have it?
- Is every year, decade and list written the same way each time?
Checking takes time you must plan for, so see the guide to managing your time in IELTS Writing. The common mistakes guide shows where punctuation sits among other faults, and the essay checker reads an essay against the criteria. Shorter sentences also have fewer places to go wrong, which the guide to concise writing for IELTS Writing covers.
Frequently asked questions
Does IELTS give a separate mark for punctuation?
No. In Writing, punctuation sits inside Grammatical Range and Accuracy, which is one of four equally weighted criteria. There is no punctuation score of its own, and IELTS publishes no count of punctuation errors allowed at any band. The descriptors describe a scale, from often wrong or missing to controlled so well that it goes unnoticed.
Is a comma splice a serious error?
It is a frequent punctuation error, and it is easy to fix, so it is worth removing. A comma splice joins two complete sentences with only a comma. IELTS publishes no penalty for any single error, but repeated splices make punctuation look unreliable, which is what the lower bands of the criterion describe.
Should I use semicolons and colons in IELTS Writing?
They are optional. IELTS publishes no list of punctuation marks you must use, and a full stop is never wrong. Use a semicolon or a colon only if you are sure of the rule, and use it sparingly. A page of correct full stops and commas reads better than a few marks used wrongly.
Can I use contractions such as "don't" in an essay?
Write them in full. This is a register point and not a punctuation rule: an essay and a formal letter are written in a formal style, so "do not" and "it is" suit them better than "don't" and "it's". IELTS publishes no list of banned forms, so this is advice, not a rule.
How do I write years and numbers in Task 1?
Write a year as digits, and put a comma after an opening time phrase, as in "In 2010, sales fell". Write a decade as "the 1990s" with no apostrophe. Use a comma in thousands, as in 1,200, and a point in decimals, as in 3.5. Choose one way of writing percentages and keep to it.
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