I just went through that.
I had to give a 30 day notice where I was, which in finance is unheard of.
Anyway, if a company and its management is worth a salt they will give you a good opportunity to tie the loose ends up.
If you're resigning because of a conflict with the management or the like, it's best to not rock the boat.
I could be more specific but I don't know all the circumstances.