JUDGMENT judgment of court was delivered by R. Sudhakar J.-The Revenue has filed this appeal calling into question order of Income-tax Appellate Tribunal "D" Bench, Chennai, dated July 22, 2011, made in I. T. A. No. 796/Mds/2010 for assessment year 2007-08, by raising following questions of law: "(i) Whether, on facts and in circumstances of case, Tribunal was right in permitting issue relating to service of notice for first time before Tribunal, which issue was not agitated before Assessing Officer or Commissioner of Income-tax (Appeals)? (ii) Whether, on facts and in circumstances of case, Tribunal was right in not applying provisions of section 292BB of Income-tax Act?" facts in nut-shell are as under: assessee filed return of income for assessment year 2007-08 admitting nil income on October 31, 2007, and same was processed under section 143(1) of Income-tax Act, 1961 (for brevity,"the Act"). case was selected for scrutiny on basis of computer assisted scrutiny system and notice under section 143(2) of Act was issued to assessee and case was taken up for hearing. 2.2. Assessing Officer, on scrutiny of records and details filed by assessee, found that assessee has not produced bills for Rs. 15,000 in respect of expenditure claimed under head "Office equipment". With regard to claim under head "Travelling and conveyance", it was found that assessee claimed Rs. 16,00,656 and out of said sum, Rs. 50,000 was disallowed, being personal in nature, and same was added to total income. Anent claim of assessee towards TDS of Rs. 1,36,290 on labour charges received from Alpump Ltd., Perungudi, Chennai, of Rs. 60,73,014, Assessing Officer, on verification of TDS certificates and records filed, held that amount received towards labour charges and credited in profit and loss account is only Rs. 56,99,791 and, therefore, added difference of Rs. 3,73,313 to total income as undisclosed business income. 2.3. Aggrieved by said order, assessee appealed to Commissioner of Income-tax (Appeals), who confirmed order passed by Assessing Officer. 2.4. assessee thereafter pursued matter before Tribunal taking legal plea that pursuant to scrutiny through Computer Assisted Scrutiny System, notice under section 143(2) of Act was served on assessee only on August 27, 2009, beyond prescribed time limit and, therefore, assessment is liable to be annulled. Even though Department pleaded that notice under section 143(2) of Act was prepared on September 18, 2008, it was found that Department has not produced any record to show that said notice was despatched and served on assessee. Tribunal, considering fact that Department issued another notice under section 143(2) of Act only on August 27, 2009, beyond time prescribed under section 143(2) of Act, held that such notice is invalid and consequential assessment is bad. 2.5. Assailing said order passed by Tribunal, present appeal is filed by Department on substantial questions of law, referred to supra. We have heard Mr. T. Ravikumar, learned senior standing counsel appearing for Department and Mr. V. S. Jayakumar, learned counsel appearing for assessee. Before adverting to merits of case, it would be apposite to refer to section 143(2) of Act, which reads as under: 143. Assessment.-...(2) Where return has been furnished under section 139, or in response to notice under sub-section (1) of section 142, Assessing Officer shall,- (i) where he has reason to believe that any claim of loss, exemption, deduction, allowance or relief made in return is inadmissible, serve on assessee notice specifying particulars of such claim of loss, exemption, deduction, allowance or relief and require him, on date to be specified therein to produce, or cause to be produced, any evidence or particulars specified therein or on which assessee may rely, in support of such claim: Provided that no notice under this clause shall be served on assessee on or after 1st day of June, 2003; (ii) notwithstanding anything contained in clause (i), if he considers it necessary or expedient to ensure that assessee has not under stated income or has not computed excessive loss or has not under paid tax in any manner, serve on assessee notice requiring him, on date to be specified therein, either to attend his office or to produce, or cause to be produced, any evidence on which assessee may rely in support of return: Provided that no notice under clause (ii) shall be served on assessee after expiry of twelve months from end of month in which return is furnished." (emphasis supplied) word "shall" employed in section 143(2) of Act contemplates that Assessing Officer should issue notice to assessee so as to ensure that assessee has not understated income or has not computed excessive loss or has not underpaid tax in any manner. It is, therefore, clear that when Assessing Officer considers it necessary and expedient to ensure that tax is paid in accordance with law, he should call upon assessee to produce evidence before him to ensure that tax is paid in accordance with law. reading of said provision makes it clear that service of notice under section 143(2) of Act within time limit prescribed is mandatory and it is not mere procedural requirement. In instant case, even though plea is taken by learned counsel for Revenue that objection in relation to non-service of notice contemplated under section 143(2) of Act was not issue before Assessing Officer and Commissioner of Income-tax (Appeals) and same was raised for first time before Tribunal, we find that it is legal plea which goes to root of matter and, therefore, assessee is entitled to raise such plea before Tribunal, which is ultimate fact finding body. In case on hand, it is beyond any cavil that assessee filed return of income on October 31, 2007. Even though Department claims to have sent notice under section 143(2) of Act on September 17, 2008, Revenue failed to produce any records to show that said notice was despatched and served on assessee. However, it is stated that Department subsequently issued another notice under section 143(2) of Act on August 27, 2009, which, on face of it, is beyond period of limitation prescribed under section 143(2) of Act. basic requirement of section 143(2) of Act having not been satisfied, Department's further proceedings, in our considered opinion, becomes non est in law. above said view of this court is fortified by decision of Supreme Court in Asst. CIT v. Hotel Blue Moon  321 ITR 362 (SC) and it was observed as under (page 369): "Omission on part of assessing authority to issue notice under section 143(2) cannot be procedural irregularity and same is not curable and, therefore, requirement of notice under section 143(2) cannot be dispensed with." In such view of matter, we do not find any substantial question of law in this appeal and accordingly, this appeal is dismissed. No costs. *** Commissioner of Income-tax v. Gitsons Engineering Co.