National Internal Revenue Code (NIRC)
Section 72. Suit to Recover Tax Based on False or Fraudulent Returns. - When an assessment is made in case of any list, statement or return, which in the opinion of the Commissioner was false or fraudulent or contained any understatement or undervaluation, no tax collected under such assessment shall be recovered by any suit, unless it is proved that the said list, statement or return was not false nor fraudulent and did not contain any understatement or undervaluation; but this provision shall not apply to statements or returns made or to be made in good faith regarding annual depreciation of oil or gas wells and mines.