Writing is a business. Every expense you have such as convention fees, hotel, car rentals, airline tickets (assuming these things are from when you went to a writing convention), ink cartridges, reams of paper, stamps & envelopes, internet connections, and tons more, can be deducted (as far as i know)
Everywhere you go, vacations included, involve your writing so that your costs (at least part of your costs) can be considered an expense. And keep good records!
Emsky, would you go down to the IRA office with me tomorrow and explain all this to them. They have an agent down there who is only interested in non-fictional tax returns. Although fiction is a lot harder to sell than non-fiction, especially to the IRS, I tried to tell him, over the telephone, that I only write fiction. He said I had that right, and that is why he wants me to come down there to his office and explain a few things. Like for starters, how one person can spend more money on postage in a month, than they make in a year. I grant you it was not an easy story to write, but I had a great ending on line 73.