A bill to insure the confidentiality of information filed by individual taxpayers with the Internal Revenue Service pursuant to the Internal Revenue Code and, at the same time, to insure the effective enforcement of Federal and State criminal laws and the effective administration of justice.

Amends the Internal Revenue Code to revise the definition of "return information." Defines as "nonreturn information" identifying information: (1) collected by the Secretary of the Treasury with respect to a taxpayer or return relating to liability for any penalty; and (2) any part of any written determination or any background file document closed to public inspection.

Allows disclosure of return information to an officer or employee of the Department of Justice for use in preparing any administrative, judicial, or grand jury proceedings involving the enforcement of a specific Federal criminal statute (but not involving tax administration) or in an investigation which may result in such a proceeding. Authorizes such disclosure only by ex parte order of a Federal district court judge or magistrate. Sets forth grounds for the granting of such order. Permits further disclosure by the Government attorney who has authorized the application for the ex parte order to Government personnel required to assist in a criminal investigation.

Requires the Secretary to disclose nonreturn information (other than nonreturn information which would identify a confidential informant or seriously impair a tax investigation), upon written request of the head or the Inspector General of a Federal agency or the Attorney General or his designee, to such officers and employees directly engaged in administrative, judicial, or grand jury proceeding involving the enforcement of a specific Federal criminal statute (but not involving tax administration) or in an investigation which may result in such a proceeding.

Permits further disclosure of such information to other Government personnel required to assist in a criminal investigation.

Directs the Secretary to disclose, as soon as practicable, nonreturn information (other than information which would identify a confidential informant or seriously impair a tax investigation) which may constitute evidence of a violation of Federal criminal laws to the extent necessary to apprise the head of the appropriate Federal agency responsible for enforcing such laws. Authorizes the Secretary, upon recommendation to the Department of Justice for prosecution for violation of the Internal Revenue Code, to disclose to the Department return information reviewed, developed, or obtained during a tax investigation which constitutes evidence of a violation of Federal criminal laws.

Allows information disclosed pursuant to this Act to be entered into evidence in a proceeding not involving tax administration or in an ancillary proceeding to which the United States is a party. Limits such disclosure to the extent required by applicable discovery requirements. Prohibits admission of such information into evidence if the Secretary determines that it would identify a confidential informant or seriously impair a tax investigation, unless a court otherwise directs disclosure.

Permits the Secretary or his designee, in specified emergency circumstances, to disclose information to the extent necessary to apprise the appropriate Federal agency of such emergency.

Permits the Internal Revenue Service to assist the Department of Justice or any other Federal agency in joint tax and nontax investigations of criminal matters which may involve tax violations.

Allows a Federal official authorized to apply to a district court judge or magistrate for an ex parte order to disclose to the appropriate State attorney general or district attorney any return or nonreturn information in his possession which is relevant to the violation of a State felony statute.

Authorizes the disclosure of return or nonreturn information to a competent authority of a foreign government which has a convention relating to the exchange of tax information with the United States. Provides a procedure for the disclosure of return or nonreturn information sought pursuant to a treaty on mutual assistance in criminal matters for use in an investigation or proceeding unrelated to the tax laws of the foreign country.

Adds as an affirmative defense to a prosecution for the unauthorized disclosure of return or nonreturn information that such disclosure resulted from a good faith, but erroneous, interpretation of this Act.

Permits a taxpayer aggrieved by the knowing or negligent disclosure by a Federal employee of return or nonreturn information in violation of this Act to bring a civil action for damages exclusively against the particular Federal agency.