How do I calculate taxes on my commission?

commissions are taxed at the same rate as wages

for help ; open the second & fifth link in: www.cut-my-tax.co.cc

Yea, you will file Sch C on that income and if the 'net' is more than $400 you will calculate you self employment tax on Sch SE, approx. 15.3% of your sch C net you need to pay estimated on 1040ES each quarter, the only ones left are Sept and Jan, next year all forms are available at www.irs.gov

It is not, and has never been, a single rate. If you had found that the same rate was being used always, that alone would prove that the wrong rate was being used. There is a schedule, but it is complicated. The easier way to calculate it is with the website http://www.paycheckcity.com using the free paycheck calculator.

You total up your income, wages plus commission, and calculate the tax on that. There's no difference between the part that was wages and the part that's commission.

If you are being paid hourly plus commission, your entire annual pay will be on your W2 form at the end of the year. That is the amount you use as your gross pay on the Federal Income Tax form.