I am competing for money using a race car. I was wondering where you could deduct the cost of racing on your taxes?

[Anita01]

If this is a hobby, meaning you don't really expect to show a profit, you would enter it as hobby income and can deduct expenses only up to your hobby income.  If it's a business, you enter the expenses under the self-employment section just as you would enter income there.  The fact that you have no income yet doesn't prevent you from entering expenses, although the IRS may reclassify it as a hobby at some point if you don't show a profit over the next 5 years.