When is it correct to use contractions in formal writing?

ScottsEnglish

Using contractions on your IELTS or TOEFL writing exam

Students often ask us here at Scott's English Success when they should use contractions (I'll, She's, They'd, it's) on their written exams. 

The short answer is, rarely. 

While contractions are very common, and even expected in oral/spoken English, and should be used during your oral exam, you should not use contractions when answering questions on the written exams. 

Writing the two words instead of the contraction shows that the writer knows the difference between spoken (informal) English and written (formal) English. 

There are a couple of exceptions (that we can think of ):  

1. IF in the IELTS GENERAL TRAINING MODULE, in TASK 1 Writing, you are asked to write a letter to a friend, you should use informal writing which would include contractions (I'm, it's, etc.)
2. In the case of  'reported speech'.  If you are quoting someone and need to quote the person correctly. For example, writing My teacher said, "I'll need to study very hard to pass my test." is correct.