Feedback is an essential form of communication between the student and teacher. Research has documented the importance of feedback in advancing student mathematical and critical thinking, with renewed recommendations to provide and use feedback in mathematical instruction during the era of COVID-19. Giving personalized feedback in an online environment can be a challenge -- especially in a mathematics class. This article summarizes five core principles of feedback, associated strategies for mathematics teachers to provide students virtual feedback, and notes on how we have implemented these strategies in middle school mathematics classes.