Training and Supervision Plan (TSP): In the first three months of your PhD you have to hand in your TSP. The requirements and templates vary between graduate schools, so please check which graduate school you belong to and what requirements they have.
Research Data Management: Certain graduate schools and departments will request you to write a Research Data Management plan. Check with your graduate school what this means to you.
Ethical approval: Some research projects should be ethically assessed by the ethics committee. E.g. projects that may involve human test subjects, can have a large impact on society, or contain personal data. To ensure the ethical principles and guidelines are met, an ethical assessment must be requested. Check with your graduate school what this means to you.
Research proposal: Writing a research proposal is strongly suggested, whether it is a requirement by your department/graduate school or not. Thinking of a good research question, summarizing your background information, setting a preliminary chapter division, and creating a timeline for your research increases your PhD trajectory. The gROW course ‘designing a PhD research project’ can possibly help you. Check with your supervisor(s) whether it’s required to write a research proposal, and if so, what it should contain.