Concealment deemed for undisclosed assets and income found in search; subsequent declaration does not avoid penalty under section 271. The amendment revises the tax base for penalty calculation by reducing assessed tax by advance tax, TDS, TCS and self-assessment tax paid before a section 148 notice, and inserts Explanation 5A to deem, for penalty under the concealment provision, that where a search discovers assets or entries representing earlier years' income for which no return was filed by the due date, any income declared in a return after the search shall be treated as concealment or furnishing inaccurate particulars.