Tax preparer and duty of performance?

Tax preparer and duty of performance?
Can a tax preparer be liable for making a mistake on a tax return? A tax preparer who I been using for years filed a return with an incorrect bank account number. He states he is not liable for the mistake. I know the common belief is that the person is responsible to review the return for accuracy and completeness, but what if the person is old and does not understand much about filling taxes. After all if people are expected to check the return for accuracy doesn't that implies that the person knows how to do their return since they are checking it for errors. and if so then what is the point of using a tax preparer.
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