Comma rules
A comma (,) marks a short pause that separates parts of a sentence: items in a list, two independent clauses joined by and/but/so, introductory words or phrases, and extra, non-essential information. Commas are never used alone to join two complete sentences; that error, a comma splice, is one of the most common accuracy mistakes in IELTS writing and speaking.
How to use comma rules
How do you use commas in a list?
Use a comma after every item in a list of three or more, except before the final item where the conjunction (and/or) already separates it. Whether you also add a comma before that final conjunction (the Oxford or serial comma) is a style choice covered on its own page; either option is acceptable as long as you stay consistent.
Short adjective lists before a noun follow the same logic: separate items with commas, but don't put a comma between the last adjective and the noun it describes.
- For breakfast I usually have toast, yoghurt and fruit.no Oxford comma before 'and', also fine
- The clinic in Manchester is clean, modern, and well organised.Oxford comma before 'and', also fine
- She wore a warm, woollen, coat.no comma between the last adjective and the noun → warm, woollen coat
When do you need a comma before 'and', 'but' or 'so'?
Put a comma before a coordinating conjunction (and, but, or, so, nor, for, yet, remembered as FANBOYS) only when it joins two independent clauses, meaning both sides could stand alone as complete sentences.
If the conjunction joins two verbs sharing the same subject, or a clause to a phrase rather than another full clause, no comma is needed; adding one there is a common over-punctuation mistake.
- I applied for the scholarship, and I also emailed the admissions office.two independent clauses joined by 'and'
- I applied for the scholarship and emailed the admissions office.one subject, two verbs, no comma needed
- The bus was late, so I missed my first class.
When do you use a comma after an introductory word or phrase?
Add a comma after a word, phrase, or clause that comes before the main clause and sets the scene for it: transition words (however, therefore), time or place phrases, and subordinate clauses that start a sentence.
The comma can usually be dropped after very short introductory phrases (two or three words) if the sentence still reads clearly without it, but keeping it is never wrong.
- However, the results were far better than we expected.
- After the interview finished, I felt confident about my chances.introductory clause before the main clause
- In the end the project succeeded.short introductory phrase, comma optional
How do you punctuate extra (non-essential) information?
Use a pair of commas to frame information that could be removed without changing the sentence's core meaning: interrupters, appositives, and non-defining details about a noun that's already identified.
If the information is essential to identifying which person or thing you mean, leave the commas out; adding them would wrongly suggest the detail is optional. (The related page on comma before 'which' covers this rule for relative clauses in full.)
- My colleague, who studied in Hanoi, now leads the design team.extra detail, removable without losing meaning
- Farah, of course, remembered everyone's birthday.interrupter framed by commas
- The engineer, who wrote the report, is on leave.if only one engineer wrote the report, the detail identifies him, no commas: The engineer who wrote the report is on leave.
What is a comma splice, and why does it cost IELTS marks?
A comma splice joins two independent clauses with only a comma and no conjunction: 'The exam was hard, I still passed it.' English never allows this; fix it with a full stop, a semicolon, or a coordinating conjunction after the comma.
Comma splices are one of the most frequent punctuation errors examiners flag under Grammatical Range and Accuracy. A single splice rarely sinks a script, but repeated splices signal weak sentence control and can hold Writing or Speaking at Band 6 even when vocabulary and ideas are strong.
- The exam was hard, I still passed it.comma splice → The exam was hard, but I still passed it. / The exam was hard. I still passed it.
- Traffic in Lagos is heavy every morning; commuters plan an extra hour.semicolon fixes the splice
- House prices have risen sharply, so young families are moving further from the city.conjunction after the comma fixes the splice
Common mistakes with comma rules
Find what is wrong in each one, then open it to check.
1I wanted to visit Istanbul, but, the flights were too expensive.What's wrong? Show the fix
I wanted to visit Istanbul, but the flights were too expensive.
Don't put a second comma directly after a coordinating conjunction; one comma goes before 'but', not after it.
2It started raining, we cancelled the picnic.What's wrong? Show the fix
It started raining, so we cancelled the picnic.
Two independent clauses can't be joined by a comma alone (a comma splice); add a conjunction like 'so', or use a semicolon or full stop.
3The manager, said the deadline was final.What's wrong? Show the fix
The manager said the deadline was final.
Don't separate a subject from its verb with a comma, even in a longer sentence; 'the manager' and 'said' belong together.
4Because the internet was down we had to reschedule the call.What's wrong? Show the fix
Because the internet was down, we had to reschedule the call.
An introductory subordinate clause (Because…) needs a comma before the main clause that follows it.
5My favourite subjects are, maths and geography.What's wrong? Show the fix
My favourite subjects are maths and geography.
Don't put a comma directly before a list that completes the sentence; only separate the items themselves, not the verb from the list.
6The workshop, that starts at nine, is fully booked.What's wrong? Show the fix
The workshop that starts at nine is fully booked.
'That' introduces essential (defining) information, so it never takes commas; commas would wrongly mark the detail as removable.
7We need bread, milk, eggs, and, butter.What's wrong? Show the fix
We need bread, milk, eggs, and butter.
List commas separate items themselves, not a conjunction from the item that follows it; only one comma belongs before 'and'.
Practise
Write your own
Write a sentence of your own with comma rules, about you, your studies or your town.
Comma rules in IELTS
Speaking
- Comma splices don't exist in speech, but their spoken equivalent (running two ideas together with no pause or linking word) has the same effect: 'The traffic was bad, I arrived late' should become 'The traffic was bad, so I arrived late.' Adding the linking word signals the same control a written comma rule tests.
- Examiners can't see your punctuation, but consistent use of a full range of coordinating and subordinating conjunctions in speech mirrors correct comma placement in writing and directly supports a higher Grammatical Range and Accuracy score.
Writing
- In Task 2, comma splices between two long independent clauses are one of the most common accuracy errors examiners note; read every 'and'-free clause boundary back and ask whether it needs a full stop, a semicolon, or a conjunction.
- Introductory linking phrases ('However,', 'As a result,', 'In contrast,') need a comma immediately after them; a Band 7 script uses this pattern confidently and consistently across paragraphs.