Grammar is an important part of the IELTS test, especially in the Writing and Speaking areas. It is also required for high scores in the IELTS test. 

In the writing section, good grammar is important for both the academic and the general training writing task 1 and 2, you will be required to use good grammar and sentence structures in order to convey your ideas clearly and effectively.

In the Speaking section, good grammar is important because you will be expected to use a variety of tenses and structures correctly to answer the questions asked, if you make grammar errors, it might affect your ability to communicate your ideas effectively and score.