aside from the tax benefits...i forgot to say something important for those us who seriously quilt and spend lots of money on things like thread.
having a tax #allows you to buy WHOLESALE IN BULK. a friend of mine who has a # (from a business) buys tan thread , king tut, for her quilting and you can't believe the price difference. she also buys bolts for backings at whole sale. sometimes we get together and share a bolt or a case of thread. sometimes we buy needles together. if two or three people do this, it really works.