The IRS will held a taxpayer responsible for all information in the tax return.
If that was just calculation error - the IRS normally finds that fast and responds to the taxpayer.
If the taxpayer hired an accountant to prepare the tax return - the responsibility of the accountant should be specified in the service contract.
In the absence of the contract - both parties should work out an appropriate solution.
If the accountant knew about incorrect information and did nothing to correct - his/her actions might be classified as a fraud.
If that was a honest mistake - the accountant may be held responsible for malpractice.
Let me know if you need any help.