JUDGMENT This writ application is directed against a judgment and order dated October 8, 1999 passed by the West Bengal Taxation Tribunal in Case No. RN 337 of 1999 whereby and whereunder the application filed by the petitioner under section 8 of the West Bengal Taxation Tribunal Act, 1987 (hereinafter and for the sake of brevity referred to as "the said Act") questioning the validity of the retrospectivity of the order dated June 3, 1999 passed by the respondent No. 1 cancelling the order dated February 5, 1999 whereby and whereunder the eligibility certificate granted in terms of section 41 of the West Bengal Sales Tax Act, 1994 for remission of the sales tax had been dismissed. The point involved in this application is an interesting one. The petitioner herein which is a registered company incorporated under the Indian Companies Act, 1956 had set up a small-scale industry within the territorial jurisdiction of the Calcutta Municipal Corporation for the purpose of manufacturing rubber goods, etc. Relying on or on the basis of the provisions contained in section 41 of the said Act the petitioner had filed an application before the concerned authority. Upon inspection of the factory of the petitioner the parties had satisfied themselves with regard to its eligibility as regards grant of sanction and passed an order on February 5, 1999 whereby and whereunder remission to the extent of 70 per cent of the amount of capital invested being Rs. 65,59,729 was granted for a period of five years. Such exemption had been granted at the first instance for the period from October 30, 1998 to October 29, 1999. The petitioner herein relying on or on the basis of the said exemption certificate did not realise any sales tax from its purchasers and had issued declaration forms to the parties and in turn on issuing such declaration the registered dealers who had purchased the aforementioned goods did not pay the sales tax to the petitioner. However, it was later on detected that as the petitioner does not come within the purview of table appended II of sub-rule (2) of rule 128 of the West Bengal Sales Tax Rules, 1995, the said order of exemption had been cancelled by an order with effect from October 30, 1998. However, it was later on detected that as the petitioner does not come within the purview of table appended II of sub-rule (2) of rule 128 of the West Bengal Sales Tax Rules, 1995, the said order of exemption had been cancelled by an order with effect from October 30, 1998. The petitioner before the Tribunal as also before us questioned the validity or legality of that part of the order of sub-rule (2) of rule 128 which reads thus : "128.(2) A registered dealer shall, unless he has once opted for tax-holiday under section 39, be eligible to enjoy the benefit of remission of tax in respect of his newly set up industrial unit located in an area, specified in column (1) of the Table appended to this sub-rule, on account of sales of the class or classes of goods manufactured in such industrial unit specified in column (2) of the said Table, and purchase of goods for use directly in the manufacture of such goods, and the tax payable by such dealer may be remitted - (a) in respect of the period specified in column (3) of the said Table, (b) for an amount not exceeding such percentage of gross value of the fixed capital assets as specified in column (4) of the said Table of seventy-five crore rupees, whichever is less." It appears from the table that maximum eligible period in respect of which payment of tax may be exempted commencing from the due date relating to the newly set up industry situate within an area under the Calcutta Municipal Corporation would be five years only in respect of electronic goods, gem, jewellery, etc., whereas in relation to the other areas any goods other than specified hereinbefore would be exempted. Evidently a mistake had been committed by the authorities in granting the aforementioned exemption. The question which arises for consideration is as to whether the said order dated June 3, 1999 can be given a retrospective effect. It is not in dispute that the only power conferred upon authorities in this regard is contained in rule 135 of the said Rules which reads thus : "135. The question which arises for consideration is as to whether the said order dated June 3, 1999 can be given a retrospective effect. It is not in dispute that the only power conferred upon authorities in this regard is contained in rule 135 of the said Rules which reads thus : "135. (1) Remission of the tax payable by a dealer in accordance with the rules contained in this Part may be discontinued even before the expiry of the eligible period as applicable to him if such dealer contravenes any of the provisions of the Act and the Rules laid down in this Part and Part VI. (2) Where the Deputy Commissioner or the Assistant Commissioner, as the case may be, has in his possession information that the dealer has contravened any provision of section 41 or the rules referred to in sub-rule (1), such Deputy Commissioner or Assistant Commissioner, shall, after giving such dealer a reasonable opportunity of being heard, pass an order for discontinuance of the benefit of remission of the tax payable by such dealer for reasons to be recorded in writing : Provided that the benefit of remission of tax shall not be refused for any period prior to the date of such contravention by the dealer unless the order granting the certificate of eligibility or renewal of such certificate is revised otherwise under section 80 or section 81, or reviewed otherwise under section 83, by a competent authority." As a general principle of law the authority passing an order under bona fide mistake can pass an order rectifying the same. However, if such an order visits the affected party with civil or evil consequence or such an order had been passed after a long time the principles of natural justice are to required to be complied with. Reference in this connection may be made in S. K. Dogra v. Union of India reported in CAL LT 1996 (1) HC 73 wherein this Court has relied upon a decision of the apex Court in Bhagwan Shukla v. Union of India reported in AIR 1994 SC 2480 . It is true that any order passed in derogation of a mandatory provisions of law would be a nullity. It is also equally true that nobody derives any right out of an illegal order but the said rule has certain exceptions. It is true that any order passed in derogation of a mandatory provisions of law would be a nullity. It is also equally true that nobody derives any right out of an illegal order but the said rule has certain exceptions. An order which had been passed without authority unless it is set aside remains valid. Furthermore, an order may be valid for one person and invalid for other person. It is also a trite law that although a provision is apparently held to be mandatory, the same may not be construed to be mandatory having regard to various factors including injustice which may be caused to the affected party. In State of West Bengal v. Anil Chandra Chowdhury reported in (2000) 1 CLJ 39 a division Bench of this Court has relied upon a decision of the apex Court in State of Punjab v. Gurdev Singh reported in AIR 1991 SC 2219 holding as under : "In the instant cases, the respondents were dismissed from service. May be illegally. The order of dismissal has clearly infringed their right to continue in the service and indeed they were precluded from attending the office from the date of their dismissal. They have not been paid their salary from that date. They came forward to the court with a grievance that their dismissal from service was no dismissal in law. According to them the order of dismissal was illegal, inoperative and not binding on them. They wanted the court to declare that their dismissal was void and inoperative and not binding on them and they continue to be in service. For the purpose of these cases, we may assume that the order of dismissal was void, inoperative and ultra vires, and not voidable. If an Act is void or ultra vires it is enough for the court to declare it so and it collapses automatically. It need not be set aside. The aggrieved party can simply seek a declaration that it is void and not binding upon him. A declaration merely declares the existing state of affairs and does not 'quash' so as to produce a new state of affairs. But nonetheless the impugned dismissal order has at least a de facto operation unless and until it is declared to be void or nullity by a competent body or court. A declaration merely declares the existing state of affairs and does not 'quash' so as to produce a new state of affairs. But nonetheless the impugned dismissal order has at least a de facto operation unless and until it is declared to be void or nullity by a competent body or court. In Smith v. East Elloe Rural District Council [1956] AC 736 at p. 769 Lord Redcliffe observed : 'An order even if not made in good faith is still an act capable of legal consequences. It bears no brand of invalidity upon its forehead. Unless the necessary proceedings are taken at law to establish the cause of invalidity and to get it quashed or otherwise upset, it will remain as effective for its ostensible purpose as the most impeccable of orders.' Apropos to this principle, Prof. Wade states : 'the principle must be equally true even where the "brand of invalidity" is plainly visible; for there also the order can effectively be resisted in law only by obtaining the decision of the court' (see : Administrative Law, 6th Ed. p. 352). Professor Wade sums up these principles : 'The truth of the matter is that the court will invalidate an order only if the right remedy is sought by the right person in the right proceedings and circumstances. The order may be hypothetically a nullity, but the court may refuse to quash it because of the plaintiff's lack of standing, because he does not deserve a discretionary remedy, because he has waived his rights, or for some other legal reasons. In any such case the "void" order remains effective and is in reality valid. It follows that an order may be void for one purpose and valid for another, and that it may be void against one person but valid against another'." (Ibid page 352). Reference in this connection may also be made to Crawford on Statutory Construction which is as follows : "Even where a statute is clearly mandatory or prohibitory, yet, in many instances, the courts will regard certain conduct beyond the prohibition of the statute through the use of various devices or principles. Most, if not all of these devices find their justification in considerations of justice. Most, if not all of these devices find their justification in considerations of justice. It is a well-known fact that often to enforce the law to its letter produces manifest injustice, for frequently equitable and humane considerations, and other considerations of a closely related nature, would seem to be of a sufficient calibre to excuse or justify a technical violation of the law." However it appears that the point at issue is directly covered by several decisions of different High Courts. In K. P. Enterprises v. Divisional Deputy Commissioner of Sales Tax, Raipur reported in [1996] 102 STC 483 (MP), A. K. Mathur, C.J., speaking for the division Bench in almost identical situation, inter alia, held as under : "................. If the authority wants to withdraw the eligibility certificate, then the effectivity of withdrawal shall be with effect from the date of order and it cannot be made retrospective. To this extent submission of learned counsel is correct that the order of withdrawal of eligibility certificate cannot be given retrospective effect and the petitioner is entitled for the relief to this extent." In that case the question which arose for consideration was as to whether the dealer was entitled to the grant of exemption from payment of sales tax on the ground that it was manufacturing certain goods to which exemption were to be granted only to a manufacturer and not to others but despite the same, the division Bench laid down the law in the aforementioned terms. Yet again in Vinytics Peripherals Private Ltd. v. Commissioner, Trade Tax, U.P., Lucknow reported in [1998] 111 STC 359, a learned Judge of the Allahabad High Court held as under : "The Commissioner should realise that for no fault of the applicant, the applicant should not be penalised for omission and commission of the department who were equally at fault in granting the eligibility certificate if according to them such certificate was not entitled by the applicant. In that view of the matter, I quash the order passed by the Trade Tax Tribunal dated May 27, 1984 as also the order passed by the Commissioner on March 27, 1993." K.P. Enterprises [1996] 102 STC 483 (MP), has been followed by a learned Judge of the Madhya Pradesh High Court in Kitchen Aid v. State of M.P. reported in [1998] 110 STC 109. Keeping in view the aforementioned decisions as also the phraseology used in the rules aforementioned we are of the opinion that as a specific power has been conferred upon the statutory authority to discontinue to grant remission of the tax which had earlier been granted in its favour even during the period for which it was eligible, in our opinion the power of the statutory authority must be held to be confined to the aforementioned extent and not to withdraw such concession with retrospective effect. We cannot lose sight of the fact that if construed otherwise various public inconvenience will ensue. As indicated hereinbefore, the petitioner has not only not realised sales tax from its purchasers, it has also not paid tax to its sellers relying on or on the basis of the aforementioned exemption certificate wherefor he had issued the requisite declaration forms. Sales tax as is well-known, in certain cases becomes payable by the dealer upon sale. Dealer in turn under section 37 of the West Bengal Sales Tax Act collects the sales tax from its customers as an agent of the State of West Bengal. Unlike income-tax, the taxable event is not the income it is on sale and once exemption is granted on payment of any tax as a result whereof the petitioner would not perform his statutory duty as envisaged under section 37 of the said Act. It is not a case where the doctrine of restitution may be taken recourse to nor is it a case where the petitioner could have been directed to pay the amount by invoking the principles of unjust enrichment. For the reasons aforementioned we are of the opinion that the learned Tribunal committed an error in passing the impugned judgment which is set aside accordingly. This application is allowed. However, there will be no order as to cost. All parties are to act on a xeroxed certified copy of the judgment, to be delivered on priority basis, on the usual undertaking. Application allowed.