When is it appropriate to call oneself MA candidate?

When you're trying to publish MS candidate is a polite way of saying you're a grad student. From what I understand as long as you're in school and working towards the degree you can hold the title "candidate" for publications and conferences. When I was in grad school and we were applying for jobs we were advised to use "candidate" to indicate we'd finished our course work and only had the thesis left (kind of like saying you're all but dissertation - ABD - when you're finishing your PhD). I don't know if that's true across the board, but that's what we were advised.