Should I write my answers in capital letters or lower case?

Reading and Listening

The answer is that punctuation is not marked in the IELTS Listening or Reading tests, so it doesn't matter whether you use capital letters (upper case) or lower case letters to write your answers.

However, if you are taking IELTS On Paper, it is advised that you write all of your answers on the Listening and Reading answer sheets in capital letters (upper case). This is because the answer sheet will be scanned, and then read and scored by computer and capital letters are usually clearer and easier to read accurately than lower case.

If you are taking IELTS On Computer, it does not matter. Use capital letters, lower case, or the normal mix.

Writing

If you are taking IELTS On Paper, you are permitted to use all capital letters. If you have serious problems with your handwriting this may be a good idea.

However, you are marked on punctuation in IELTS Writing. This includes the correct use of capital letters (upper case) and lower case. So you should try to write using normal punctuation if possible.