Q. How do I avoid self-plagiarism?

Double submission of your own work is a form of self-plagiarism.

This may take the form of copying either the whole piece of work or just part of it. Normally credit will have already been given for this work when the work was submitted the first time. This includes double submission of any assessed work, including your essays, posters, presentations, own diagrams or infographics, etc.

Occasionally referring back to a previous assignment (with proper referencing and acknowledgement) might be permitted, if you are building on your original piece of work. You must think very carefully before referencing your own assignments and if in any doubt check with the course tutor that it's OK to do so.

The Library tutorial on Understanding Plagiarism covers double submission.