What documents do I need to submit when registering an NPO with the Registrar General?

We’ve finally decided to register our organisation properly. We’ve been operating informally for about two years and now a potential donor is asking for our registration certificate before they’ll consider us for funding. I went to the Registrar General’s website and honestly it’s not very clear about exactly what we need to bring. Do we need a constitution? ID for all the directors? Is there a form we fill out there or do we prepare it in advance? If anyone has gone through this process recently I’d love to hear what it was actually like — what you brought, how long it took, any surprises.