That's exactly what my accountant told me. He said we do the best we can and if the IRS doesn't like it, they'll let us know. He said there are so many ambiguities in the tax law that no one can ever be 100% sure that they did some things correctly. Many times the IRS disagrees and goes after a company. Then the company fights it in court and the ruling goes against the IRS. A law can't be proven right or wrong until it is challenged in court and a ruling is forthcoming. My accountant said it is more important to not have your tax liability change than it is to be right or wrong.
Bob