From this blog post: https://tylerburleigh.com/mturk/ethical-survey-withdraws-add-a-withdraw-button-to-qualtrics-surveys/ "When conducting survey research online using MTurk, researchers are under an ethical obligation to give participants the ability to withdraw from a study without incurring a financial penalty. In practice, however, this is often not the case. In most of the academic Qualtrics surveys I’ve seen, researchers tell participants something to the effect of: “you can withdraw at any time by exiting the survey (e.g., by closing your web browser or navigating away from the survey)”. Most academic researchers also use the Survey Completion Code mechanic, whereby participants must reach the end of the survey to receive a unique code that they submit to MTurk for compensation. Taken together, these two elements create a situation where, if participants withdraw by closing their browser or navigating away, then they will not receive compensation for their participation. Arguably, this creates a financial penalty for withdrawing—the penalty of not receiving payment—and thus an ethical dilemma. This dilemma can be avoided by adding a withdraw button in the survey that, once clicked, will take participants to the end of the survey (or a custom withdraw page) where they may still obtain a completion code. Qualtrics doesn’t have this functionality baked-in, but fortunately it’s pretty easy to implement. In this tutorial, I describe the method that I use."