Reflections on seeking a publisher 3: Write the proposal before the book?

Before I started the proposal process for my book, I had written a complete draft (as well as two almost-complete early drafts), and also hired an editor to check that draft. I had, in short, a pretty mature draft. But the questions publishers ask about the completeness of the draft, led me to wonder whether that was the best plan for seeking publication.

Common proposal questions ask: “When do you plan to finish the book?”, and “When can you deliver the manuscript?”, which seem primarily relevant for proposals written by people who have not yet completed their book.