In what cases are you able to start a postdoc without a "conferred" PhD?

Many PhD programs only confer their degrees one, two or three times per year. If you successfully defend and submit your dissertation after the scheduled conferral date, you must wait until the next one to get the PhD. At many of these schools you can ask for an official document that basically states that all requirements for the PhD have been successfully completed and the degree will be conferred on the next conferral date.

Do postdoctoral research positions accept this type of official document in lieu of a PhD, to begin work, if a PhD is required? Is this specific from position to position or country to country? I will be receiving a PhD in the US and looking for postdocs in either the US, Canada, Europe, Japan or Australia.