Provided that where an assessment under sub-section (3) of section 143 or this section has been made for the relevant assessment year, no action shall be taken under this section after the expiry of four years from the end of the relevant assessment year, unless any income chargeable to tax has escaped assessment for such assessment year by reason of the failure on the part of the assessee to make a return under section 139 or in response to a notice issued under sub-section (1) of section 142 or section 148 or to disclose fully and truly all material facts necessary for his assessment, for that assessment year:

Provided further that nothing contained in the first proviso shall apply in a case where any income in relation to any asset (including financial interest in any entity) located outside India, chargeable to tax, has escaped assessment for any assessment year:

Provided also that the Assessing Officer may assess or reassess such income, other than the income involving matters which are the subject matters of any appeal, reference or revision, which is chargeable to tax and has escaped assessment.

Explanation 1.—Production before the Assessing Officer of account books or other evidence from which material evidence could with due diligence have been discovered by the Assessing Officer will not necessarily amount to disclosure within the meaning of the foregoing proviso.

Explanation 2.—For the purposes of this section, the following shall also be deemed to be cases where income chargeable to tax has escaped assessment, namely :—

(a)  where no return of income has been furnished by the assessee although his total income or the total income of any other person in respect of which he is assessable under this Act during the previous year exceeded the maximum amount which is not chargeable to income-tax ;

(b)  where a return of income has been furnished by the assessee but no assessment has been made and it is noticed by the Assessing Officer that the assessee has understated the income or has claimed excessive loss, deduction, allowance or relief in the return ;

(ba) where the assessee has failed to furnish a report in respect of any international transaction which he was so required under section 92E;

(c)  where an assessment has been made, but—

  (i)  income chargeable to tax has been underassessed ; or

 (ii)  such income has been assessed at too low a rate ; or

(iii)  such income has been made the subject of excessive relief under this Act ; or

(iv)  excessive loss or depreciation allowance or any other allowance under this Act has been computed;

(ca) where a return of income has not been furnished by the assessee or a return of income has been furnished by him and on the basis of information or document received from the prescribed income-tax authority, under sub-section (2) of section 133C, it is noticed by the Assessing Officer that the income of the assessee exceeds the maximum amount not chargeable to tax, or as the case may be, the assessee has understated the income or has claimed excessive loss, deduction, allowance or relief in the return;

(d)  where a person is found to have any asset (including financial interest in any entity) located outside India.

Explanation 3.—For the purpose of assessment or reassessment under this section, the Assessing Officer may assess or reassess the income in respect of any issue, which has escaped assessment, and such issue comes to his notice subsequently in the course of the proceedings under this section, notwithstanding that the reasons for such issue have not been included in the reasons recorded under sub-section (2) of section 148.

Explanation 4.—For the removal of doubts, it is hereby clarified that the provisions of this section, as amended by the Finance Act, 2012, shall also be applicable for any assessment year beginning on or before the 1st day of April, 2012.