The IRS made it crystal clear to me long ago. The tax filer is responsible for everything on the tax return, regardless of the preparer. Of course, accountants can be liable in other ways, but the filer has to pay the fines if the accountant makes a mistake.
From the IRS' point of view, the tax-payer is responsible for paying all of it. You can then turn around and sue to recover any of the fees/fines or penalties incurred as a result of an error made by the accountant, not the actual taxes though.
