It can take a huge chunk out of your earnings. Discuss ways, if any, to legally minimize this tax with your accountant. A little planning can save a great deal of money. When you send invoices, order inventory, buy new equipment, etc, can all have an impact on your taxes. Discuss when your fiscal year should be as well.
Accountants do more than just prepare tax forms.
They can help you understand financial and tax implications of your business decisions. Surprise your accountant and make an appointment for a tax discussion. You'll find they've got a lot more time for you now than they do on April 10.