Filling out the Spousal/Settlement Visa application...

Just a couple questions about how to fill out this online application.

Despite being an application for settlement, it requires you to input a date to 'leave the UK'. What should we put here? Is this just a flaw in the application?

Also, what kind of documents do I need to supply demonstrated our financial circumstances. Three month bank statements and payslips, I assume, but anything else?

Any tips from someone who has done this would be great! Thanks!