The IELTS, known as the International English Language Testing System, is a standardized English language proficiency exam. It measures the individual's language abilities in writing, reading, listening, and speaking. Moreover, this exam is an International English language assessment exam, so it accepts British, American, Australian, and any other English accent. However, you cannot use both or mix up British English and American English when taking the IELTS, and you need to choose only one English language.