Choice "C" is correct. Upon discovery of an error in a previously-filed return or the client's failure to file a required return, the tax practitioner should promptly notify the client (either orally or in writing) of the error, noncompliance, or omission and advise the client of the appropriate measures to be taken (e.g., advise the client to file the tax return). If the client does not rectify the error, the tax practitioner should consider withdrawing from the engagement. Choice "b" is incorrect. The tax practitioner is not barred from preparing the current year's return.Choice "d" is incorrect. The tax practitioner is not required to notify the IRS of the error.Choice "a" is incorrect. The tax practitioner is not required to file an amended return but should consider withdrawing from the engagement is the client refuses to do so.