Most migration trouble traces back to a question nobody asked in week one. This is the list I run through before agreeing to a date, grouped by what each answer protects you from.
The short version. Five questions decide the project: what success is, who signs, who decides, what happens if it goes wrong, and what happens to work created during the gap.
What does success look like?
Before reading on, try answering it for a project you are on now. Harder than it sounds, isn't it.
Push until it is countable. "All active clients available on day one, visit history back to 2019, documents attached to the right client, no client appearing twice." Every one of those is checkable, which means every one becomes a line in reconciliation.
