For social security tax you are liable for the employee half as you always have been, but you are also responsible for the employer half. However, you can deduct half the employer portion on the form you use to calculate social security tax liability. This can be especially important in a year when you might elect to take a Section 179 write-off. Washington State has a Business and Occupation tax, although it has a pretty high exemption for small businesses. Indiana has a gross receipts tax.
Many states have a state income tax.
There is also the business license. You need one from the state and another from the city in which you live. You may also need one for the other cities in which you do work even if you don t live there. Depending on what you consult on you may also need professional registration. Since you are self-employed you are not covered by unemployment insurance.