I've written about some of the more interesting tax cases I've done:
Cullather. A case about a newer Affordable Care Act tax.
Klimov. A curious NYC residency audit.
Merdjanoff. An interesting international tax case.
Sauer. There was Red Bull involved...
Kosofsky. Why punctuation matters...
Besides these, I keep track of my success rate in Tax Court.
Average reduction per case (dollar amount): $57,056
Average reduction per case (percentage): 75%
Cases which saw some reduction (percentage): 96%
Of course, very few cases even end up in Tax Court. But it gives you an idea...
This table of course only represents one type of dispute and it doesn't include cases where clients withdrew or otherwise canceled services. Nonetheless, it gives a general idea of what to expect.