IELTS grammar: How to write complex sentences

Complex sentences in IELTS writing.

Updated:  May 2024

It is important to use some ‘complex sentences’ in IELTS writing task 2 otherwise you are unlikely to get a band 6 or more in grammar. However, not all of your sentences have to be  ‘complex‘ you need to use simple sentences too.

Grammar accounts for 25% of your marks in the writing tasks but there is some confusion in IELTS about what a ‘complex sentence’ actually is.

Should you focus on grammatical range or accuracy? This is a common question, I would advise focussing on accuracy first, and when you have developed more confidence work on your range. If you have a wide range of grammar but it is inaccurate then it’s useless.

In this post we are going to look at:

1. Points to consider about complex sentences.

2. Understanding independent and dependent clauses

3. How to construct complex sentences using various grammar structures.

Key point: You need to be able to use complex sentences naturally. I advise working on these with a grammar book or a teacher long before you take your IELTS test. Just keep them concise and do not complicate it. Here is a blog post about being concise

In the following examples, I have taken sentences from IELTS exam topics such as Crime, Environment, Health issues, Technology, and Society.

1. Important points to consider about complex sentences.

First of all, let’s clear up 2 common myths that lead to confusion about ‘complex sentences’.

1. You need to impress the IELTS examiner with complicated and sophisticated grammar.

No…in fact ‘complex’ sentences are not as complex as you might think. A complex sentence is 2 or 3 simple clauses that are linked together to make 1 sentence.

2. You need lots and lots of complex sentences throughout the whole essay.

Not really …. The Band descriptors or marking scheme say that you need to ‘use a variety of complex structures’ and have ‘grammatical range and accuracy.’ This doesn’t mean that the whole essay has to have lots of these sentences. As long as you have a few in the essay mixed with simple sentences and they are clearly understood then that is fine. Of course, if you want a band 8 or 9 then they need to be more sophisticated.

As I mentioned in point 1 above, many people try to use long confusing sentences hoping they sound interesting or impressive but they end up confusing the examiner. ‘Complex’ in this case does not mean ‘Complicated’.

2. Understanding dependent and independent clauses.

Before going into detail about complex sentences it is important to know what independent and dependent clauses are. A clause is a group of words with both a subject and a verb.

Example of a dependent clause:   ……. because the car broke down

This just doesn’t make much sense because a dependent clause relies on another sentence to make it coherent. So we need an independent clause to go with that.

Example of an independent clause:       I walked to work……

An independent clause makes sense on its own, it doesn’t need other sentences to be understandable.

So now we have:  ‘I walked to work because the car broke down’. I can also reverse this using a comma after the dependent clause: ‘Because the car broke down, I walked to work. ‘

Was that complicated?…. OK, let’s get into some more detail and try out different grammar structures now.

3. Using various grammar structures.

Compound sentences:

These are made of two independent clauses joined by a coordinator such as for, and, nor, but, or, yet, so. A comma is needed before these words. These simple sentences make sense when they are on their own. When we put them together with the coordinator they become compound sentences.

I work in an office, and she works in a shop.

I work late, but she finishes early.

He doesn’t like his job, yet he always works hard.

But this is not a compound sentence: He doesn’t like his job but works hard.  This is just a simple sentence.


Subordinate clause and main clause:

These are constructed by connecting an independent clause with a dependent clause. You need to use subordinate conjunctions like: unless, even though, although, while, because, when, if, whereas, since, whether, until…..

The government must take action on factory emissions. The problem of pollution will get worse.

Here are 3 examples with the subordinate conjunction Unless, Until and If... notice that I use a comma after the dependent clause… also notice the word take becomes third person singular. in example 3 the independent clause comes first.

Unless the government takes action on factory emissions, the problem of pollution will get worse.

If the government does not take action on factory emissions, the problem of pollution will get worse.

The problem of pollution will get worse until the government takes action on factory emissions.


Compound complex sentences:

These types of sentences contain two independent clauses and a dependent clause. They contain both coordinators and subordinators.


Relative clauses:

These give extra or important information about a thing, a place, or a person using which, that, who, where, whose. For example. A man lives next door. He is a carpenter. We can just join the sentences with ‘who’ … The man who lives next door is a carpenter.

Modern cities are polluted. This leads to asthma and other health conditions. This is caused by fumes from heavy traffic.

By using which I can connect the three sentences. I have also used the passive in this sentence: .. is caused by.

Pollution in modern cities is caused by fumes from heavy traffic, which leads to asthma and other health conditions.

Let’s try another one.

Crime in modern cities is a big problem. One reason is the increase in social inequality.

Now I will use ‘that’ to join the sentences together, notice how I have moved the sentences around.

The increase in social inequality is one reason that crime in modern cities is becoming a big problem.


Gerunds are verbs with – ing, such as:  shopping is a popular pastime, or Parking is becoming a problem in city centres…  Gerunds are very useful when writing essays.

Obesity can cause several health problems. Obesity leads to heart problems and diabetes.

I can change the wording, add a gerund, and also use the words ‘such as’ to show an example.

Being overweight can cause several health problems, such as heart disease and diabetes.

I used the word overweight to replace obesity and started with a gerund,’ being...’. By using a relative clause it makes a simple clear ‘complex’ sentence.


Conditional clauses:

These are quite useful and can be used to propose some solution to a problem much the same way as you would use unless. For example: If the government does not take action soon, then the problem will get worse.

There are a few types of conditionals:

The 1st conditional expresses a possible or real outcome.  If + present tense + will

If action is not taken soon on climate change, global warming will get worse.

The 2nd conditional expresses a hypothetical outcome.  If + past tense + would

If the public were made aware of the problems of smartphone addiction, a lot more people would seek help.

The 3rd conditional expresses a hypothetical past. If + had + past participle + would have / could have / may have

If the internet hadn’t been invented, the world wouldn’t have instant communication as is so common nowadays.

To see a full lesson on conditional sentences click here.

The best advice is to work on your grammar especially relative clauses, gerunds, conditionals, ‘unless’ statements, prepositions, and articles. Try to keep it simple, you should not write overly complicated sentences or you will lose points.

Many IELTS teachers complain that students write essays which are so difficult to understand due to over-complex grammar use. You can see a recent lesson on this by clicking here.


Leave a comment below if you have any questions.

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