Usage of Complex sentences in IELTS

Complex sentence is understood in a wrong way by many students. Often the word complex is assumed as a complicated, long, and impressive.  Most of the students might have ideas of using complex sentence to get higher band in IELTS writing or speaking, however, based on their understanding they tend to write long and grammatically incorrect answer that are hard to understand.

Let’s look at the overly complex sentence example by Mark Twain:
At times he may indulge himself with a long one [sentence], but he will make sure there are no folds in it, no vagueness, no parenthetical interruptions of its view as a whole; when he has done with it, it won’t be a sea-serpent with half of its arches under the water; it will be a torch-light procession. This sentence contains 58 words and it is kind of puzzle to the readers.

Writing simple sentences will not increase your band nor can the complex sentence like Mark Twain example.

So, what is complex sentence and how to write complex sentence to get better sore in IELTS writing and speaking?  
Complex sentences is not more than two sentences combined together to make one a sentence. It contains one independent and two or more dependent clauses.

Know more about Dependent and Independent clauses.

For instance: Although it was a summer vacation, John kept doing his academic tasks because he got exam right after his vacation because he have got exam right after his vacation.

Dependent clause – Although it was a summer vacation
Independent clause – John kept doing his academic tasks
Dependent clause - because he has got exam right after his vacation.
Dependent clause begins with sub-ordinate conjunctions and I have used two sub-ordinates conjunctions in the above example. If you write dependent clause before independent clause, place comma before starting an independent clause otherwise, punctuation is not needed.

Uses of complex sentences in IELTS writing and speaking:
Generally, usage of simple sentence while making main points, at the beginning of the paragraph and jumping to complex sentences while expanding the main point is better for IELTS.

For example:
Overweight has become one of the greatest problems of this era which cannot be overlooked. In my opinion, the problem of overweight arises from the consumption of the junk food. Although, the calories in junk food are clearly written in the packages, people don’t stop themselves from eating junk food.   

First sentence is the topic sentence and makes main point.
In my opinion is used to give strong, clear, and strong personal view in second sentence.   
In third sentence, there are one dependent and one independent clause combined together to make complex sentence and it is expanding the main point.