This is one of the most frequently asked questions we receive and unfortunately there’s no single or simple answer. We have written a few posts about the ethics of proofreading for students so there is more detail in those but the simplest answer to the above question is for you to check with your university or education institution. Even then, some departments or schools within a university might have different rules so it might be best to check with your supervisor. In our experience, most universities are happy for students to get their work proofread but not all are, and some also have specific guidelines for the proofreader to consider.
