If it is your first year of paying your own self employment tax, you won't have much of a basis to go on, but I just got done with my taxes for the year 2007, and the self employment tax is at least as much as the income tax. Normally you base your quarterly payments on the previous years totals. But definitely, the income tax is only half of what you'll pay next April. Unless you're making a lot, the self employment tax (social security) is 15.3% of your net profits. And I'm also somewhere near 15 percent on the income tax level too. So added together, you get that 1/3 of your income Don mentioned going to the IRS.
