How do I determine my target market for an accounting and tax service business?

I'm trying to compile a business plan for the creation of an accounting and tax business. In the market analysis section of my business plan, I want to define my target markets, but I'm having trouble doing so. I need some guidance.

Some good places to start would be people, then businesses, then nonprofits, then geography. That list is not exclusive, but helps you segment.

In terms of people, will you work with tax filers, sole proprietors or both? Will you focus on businesses? If so, what kind? Medical offices? Construction companies? Will you offer a range of
services for nonprofits? If so, which ones? What about geography? Will you work with companies all over or just on the north side of town?

Ideally, this exercise will allow you to focus on one or two segments that you can really market to and go after.

All the best
Brad Sugars