So many IELTS candidates have asked me this question when they couldn't clear their writing hurdle. They are mostly those who either need to score a 7 in each of the 4 modules or aspirants requiring the minimum score that qualifies for the Canada Express Entry Programme: 8,7,7,7 - with 8-band being in Listening and 7-band each in Speaking, Reading, and Writing. And my answer has always been the same: if you followed certain things, you should send your paper for a remark. Else, forget it and go back to the drawing board.
First, you must understand that it is not necessary that you should get a 7 in writing just because you did so well in the other three modules. Writing is an altogether different kettle of fish and you have to follow the basic principles of good writing to secure your required band in this module.
did you complete all the tasks that you were expected to do in both the Letter and the Essay?
Did you elaborate on the points sufficiently? Did every paragraph lovingly dwell on each point mentioned therein before proceeding to the next one?
Were you always relevant and to the point? Or did you write something which may safely be removed without making any difference to your answer?
Did you repeat anywhere? Repetition of words, phrases, points, sentence structures, even sounds maybe?
Were basic grammar rules followed and did your writing exhibit a fairly wide range of sentence structures - a mix of complex, compound and simple sentences?
Were the paragraphs balanced? - all of them roughly of the same length?
In the essay, did you give your answer in the introduction with reasons; then elaborate those reasons in the body; and finally restate your answer in the conclusion?
Was handwriting so bad as to be illegible? If not, it’s not a factor.
If you did all the above, then you should have got a 7-band. In such a case, get it re-evaluated. Makes no difference - never did - if it was an IDP or a British Council test center from where you had given your attempt.