How exactly do you write a proposal for deferment?

<p>I'm planning on deferring my admission next year, and since tomorrow is the national reply date, I need to write my proposal ASAP. (Btw, I'm not lazy - I just found out today that I've been accepted to a year-long program.) I get the basic gist, but is it supposed to have a specific format? Formal writing? Or is it just a casual explanation of why you're defering?</p>