The IELTS test is a British test created by UCLES (University of Cambridge Local Examination Syndicate) in the UK. It is written in British English.

Since the IELTS is an international test, the vocabulary and syntax used will be completely understandable to anyone who has studied English in an English-speaking country. If you don’t recognize a word at first, you will be able to assess the meaning of the word through its context in the sentence. In addition, you do not have to use British English in the writing module. However,you must use just one form of English consistently—that is, either British or American when writing the exam.