IELTS examination writing in particular, are assessed manually by a certified IELTS examiner. They assess with certain format which is being mandatory for task 1 and task of both general and academic writing. Task 1 of general has letter writing where the tone of the letter is given first preference as the candidate should be aware whether the letter is formal, semi-formal or informal and the tone should be maintained accordingly till the end. Following that, the task 1 of academic which tends to be a formal representation of an image, must be well organized into three paragraphs, furthermore, it should cover maximum data has possible and interpretations along with comparisons are to be made.
General and academic task 2 writing has an argumentative essay which may be of advantages - disadvantages or problems causes and solutions. Accordingly, the essay should be organized with introduction followed by body part and conclusion. Essays are never to be less than the intended 250 words; else the candidate will be penalized as the examiner provides high priority for it. Then, the content which is to be always taken care as it plays a vital role in framing the structure of the essay. Candidates should take into account that grammar acts as a backbone for writing tasks and they should use all the three sentence structures. Tenses should be utilized with cautions according to the content that at which time line does the situation happens. Following all this will provide a band 9 essay to the candidate.
References
https://www.ieltsadvantage.com/2015/09/02/ielts-band-9-essay/
https://www.oxfordonlineenglish.com/ielts-writing-task-1-general-band-9