Can I submit an abstract for an unwritten paper which will form part of my PhD? I am applying for my PhD to start this Autumn. There is a conference coming up soon with a theme which is very relevant to my PhD topic and I would like to submit an abstract for it, write the paper and then develop parts of it for my PhD at a later stage. Is it OK to write a paper for the conference and then later use parts of it for my PhD seeing as it is so relevant?

EDIT: For a little more information, this is for a conference on music and the research has not been carried out yet. Additionally, the area that is being researched is one that has very little scholarly coverage. Due to this, the focus will not be so much on looking for a particular kind of result, but any result that will arise from literature review/qualitative interview data. Interviews have not been conducted but there is quite a bit of time to do so, I feel. I understand if this were a scientific conference that submitting an abstract would be a little risky, but seeing as this is the humanities, I think there is more room for interpretation.
I think norms probably vary by field.  In my experience, this would be totally fine.

I work in a business school, and the expectation is that various parts of the dissertation will be published both while and after you work on the PhD.  Doctoral students also present intermediate results from their dissertation work at conferences to get feedback.

However, do be sure that the conference does not take copyright for the work presented, or you may tie your hands in terms of publication later.