Tax Court Success Rate
Besides these, I keep track of my success rate in Tax Court so that clients have an idea of what to expect. These are the results of petitions filed after receiving a notice of deficiency.
Average reduction per case (dollar amount): $58,856
Average reduction per case (percentage): 76%
Cases which saw some reduction (percentage): 95%
This table of course only represents one type of dispute; it doesn't include state or local cases, or case which were resolved with the IRS without the need to file a petition. (which is most of them) It also doesn't include cases where clients withdrew or otherwise canceled services. Nonetheless, it gives a general idea of what to expect.