Write it for someone who knows nothing
A handover document is not a list of things you already know -- it is a tool that lets someone with zero context take over your work immediately. Information that feels "obvious" to you is exactly what gets left out most often, so it helps to write as if you were the one starting the role for the first time.
Start the draft even without a named successor
If a successor has not been assigned yet, do not wait to start writing. Finish the document as soon as your move or departure is confirmed and hand it to your manager or team lead. That way it is ready to pass along the moment someone is assigned, and there is no gap where nobody has the information.
Frequently Asked Questions
How soon before I leave should I start writing the handover document?
Start drafting as soon as your departure or transfer is confirmed, and aim to have a finished version ready a few days before your actual handover date, leaving room for questions.
What should I do if a successor has not been assigned yet?
Finish the document anyway and pass it to your manager or team lead. That way it can be handed off the moment someone is assigned, minimizing any gap in coverage.