(1)  An appeal shall lie to the National Tax Tribunal from every order passed in appeal by the Income-tax Appellate Tribunal and the Customs, Excise and Service Tax Appellate Tribunal, if the National Tax Tribunal is satisfied that the case involves a substantial question of law.

   (2)  The Chief Commissioner or the Commissioner of Income-tax or the Chief Commissioner or Commissioner of Customs and Central Excise, as the case may be, or an assessee aggrieved by any order passed by the Income-tax Appellate Tribunal or any person aggrieved by any order passed by the Customs, Excise and Service Tax Appellate Tribunal (hereinafter referred to as aggrieved person), may file an appeal to the National Tax Tribunal and such appeal under this sub-section shall—

   (a)  be filed within one hundred and twenty days from the date on which the order appealed against is received by the assessee or the aggrieved person or the Chief Commissioner or Commissioner, as the case may be;

   (b)  be in the form of a memorandum of appeal precisely stating therein the substantial question of law involved; and

   (c)  be accompanied by such fees as may be prescribed:

   Provided that separate form of memorandum of appeal shall be filed for matters involving direct and indirect taxes:

   Provided further that the National Tax Tribunal may entertain the appeal within sixty days after the expiry of the said period of one hundred and twenty days, if it is satisfied that the appellant was prevented by sufficient cause from preferring an appeal in time.

   (3)  Where an appeal is admitted under sub-section (1), the National Tax Tribunal—

   (a)  shall formulate the question of law for hearing the appeal; and

   (b)  may also determine any relevant issue in connection with the question so formulated—

   (i)  which has not been so determined by the Income-tax Appellate Tribunal or by the Customs, Excise and Service Tax Appellate Tribunal; or

   (ii)  which has been wrongly determined by the Income-tax Appellate Tribunal or by the Customs, Excise and Service Tax Appellate Tribunal,

and shall decide the question of law so formulated and the other relevant issue so determined and deliver such judgment thereon containing the grounds on which such decision is founded and may award such cost as it deems fit.

   (4)  Where in any appeal under this section, the decision of the Income-tax Appellate Tribunal or the Customs, Excise and Service Tax Appellate Tribunal involves the payment of any tax or duties, the assessee or the aggri

eved person, as the case may be, shall not be allowed to prefer such appeal unless he deposits at least twenty-five per cent. of such tax or duty payable on the basis of the order appealed against:

   Provided that where in a particular case the National Tax Tribunal is of the opinion that the deposit of tax or duty under this sub-section would cause undue hardship to such person, it may dispense with such deposit subject to such conditions as it may deem fit to impose so as to safeguard the interest of revenue.