Summarize the following court judgment. vil Appeal No. 1826 (N) of 1974. From the Judgment and Order dated 6.4.1972 of the Madhya Pradesh High Court in F.A. No. 23 of 1966. M.V. Goswami for the Appellants. U.A. Rana and S.K. Agnihotri for the Respondents. The Judgment of the Court was delivered by SAIKIA	 J. This plaintiffs ' appeal by special leave is from the appellate Judgment of the Madhya Pradesh High Court dismissing the appeal upholding the Judgment of the trial court dismissing the plaintiffs ' suit on the ground of limitation. A registered firm Rai Saheb Nandkishore Rai Saheb Ju galki 599 shore (Appellants) was allotted contracts for manufacture and sale of liquor for the calendar year 1959 and for the subsequent period from 1.1. 1960 to 31.3. 1961 for Rs.2	56	200.00 and Rs.4	71	900.00	 respectively	 by the Government of Madhya Pradesh who also charged 7 1/2 per cent over the auction money as mahua and fuel cess. As writ petitions challenging the Government 's right to charge this 7 1/2 per cent were pending in the Madhya Pradesh High Court	 the Government announced that it would continue to charge it and the question of stopping it was under consid eration of the Government whose decision would be binding on the contractors. The firm (appellants) thus paid for the above contracts a total extra sum of Rs.54	606.00. On 17.10.1961 the Under Secretary to Government	 M.P.	 Forest Department	 Bhopal wrote the following letter No. 10 130 X/61 (Exhibit D 23) to the Chief Conservator of Forests	 Madhya Pradesh	 Rewa: "Subject: Levy of cess on liquor contractors. Under former M.P. Government (Forest Depart ment) memo No. 4595 CR 73 XI dated 25th July	 1953	 a royalty at 7 1/2 per cent of the license fee for liquor shops was imposed on liquor contractors to cover the value of mahua & fuel extracted from the reserved or protect ed forests by the contractors for their still. The M.P. High Court has since decided that the levy of the aforesaid cess is illegal and the cess cannot be recovered from the liquor contractors. In pursuance of this decision	 Government desires that all process es whenever issued or proceedings instituted against liquor contractors for recovery of the mahua or fuel cess should forthwith be with drawn and no revenue recovery certificates should be issued in respect of this cess. Simultaneously no free supply of mahua or fuel should be permitted by virtue of the imposition mentioned above. Immediate compliance is requested. No . . X/61 Dt. Bhopal the . . 661 Copy forwarded for immediate compliance to: 600 1. Conservator of Forests	 Bilaspur. 2. All Divisional Forest Officers	 Bilaspur Circle. Copy to C.F. Raipur Circle for similar auction in this cess levied in any division of his Circle. " On 24.4.1959 the Madhya Pradesh High Court 's Judgment in Surajdin vs State of M.P.	 declaring the collection of 7 1/2 per cent illegal was reported in 1960 MPLJ 39. Even after this decision Government continued to charge 7 1/2 per cent extra money. Again on 31.8. 1961 the High Court of Madhya Pradesh in N.K. Doongaji vs Collector	 Surguja	 decided that the charging of 7 1/2 per cent by the Government above the auction money was illegal. This Judgment was reported in 1962 MPLI 130. It is the appellants ' case that they came to know about this decision only in or about September 1962. On 17.10. 1964 they served a notice on Government of Madhya Pradesh under section 80 of the Code of Civil Procedure request ing the refund of Rs.54	606.00	 failing which	 a suit for recovery would be filed; and later they instituted Civil Suit No. of 1964 in the court of Additional District Judge	 Jabalpur on 24.12.1964. The Government resisted the suit on	 inter alia	 ground of limitation. The trial court taking the view that Articles 62 and 96 of the First Schedule to the Limitation Act	 1908 were applicable and the period of limitation began to run from the dates the payments were made to the Government	 held the suit to be barred by limi tation and dismissed it. In appeal	 the High Court took the view that Article 113 read with section 17	 and not Article 24	 of the Schedule to the 	 was applicable; and held that the limitation began to run from 17.10. 1961 on which date the Government decided not to charge extra 7 1/2 per cent on the auction money	 and as such	 the suit was barred on 17.12. 1964 taking into consideration the period of two months prescribed by section 80 of the Code of Civil Procedure. Consequently	 the appeal was dismissed. The appellants ' petition for leave to appeal to this Court was also rejected observing	 "it was unfortunate that the peti tioners filed their suit on 24.12. 1964 and as such the suit was barred by time by seven days." Mr. M.V. Goswami	 learned counsel for the appellants	 submits	 inter alia	 that the High Court erred in holding that the limitation started running from 17.16.1961 being the date of the letter	 Exhibit D 23	 which was not communi cated to the appellants or any other contractor and there fore the appellants had no opportunity to know 601 about it on that very date with reasonable diligence under section 17 and the High Court ought to allow atleast a week for knowledge of it by the appellants in which case the suit would be within time. Counsel further submits that the High Court while rightly discussing that section 17 of the was applicable	 erred in not applying that section to the facts of the instant case	 wherefore	 the impugned Judgment is liable to be set aside. Mr. Ujjwal A. Rana	 the learned counsel for the respond ent	 submits	 inter alia	 that 17.10.2961 having been the date on which the Government finally decided not to recover extra 7 1/2 per cent above the auction .money	 the High Court rightly held that the limitation started from that date and the suit was clearly barred under Article 24 or 113 of the Schedule to the ; and that though the records did not show that the Government decision was communicated to the appellants	 there was no reason why they	 with reasonable diligence	 could not have known about it on the same date The only question to be decided	 therefore	 is whether the decision of the High Court is correct. To decide that question it was necessary to know what was the suit for. There is no dispute that 7 1/2 per cent above the auction money was charged by the Government of Madhya Pradesh as mahua and fuel cess	 and the High Court subsequently held that it had no power to do so. In view of those writ peti tions challenging that power	 Government asked the contrac tors to continue to pay the same pending Government 's deci sion on the question; and the appellants accordingly paid. Ultimately on 17.10.1961 Government decided not to recover the extra amount any more but did not yet decide the fate of the amounts already realised. There is no denial that the liquor contracts were performed by the appellants. There is no escape from the conclusion that the extra 7 1/2 per cent was charged by the Government believing that it had power	 but the High Court in two cases held that the power was not there. The money realised was under a mistake and without authority of law. The appellants also while paying suffered from the same mistake. There is therefore no doubt that the suit was for refund of money paid under mistake of law. The question is what was the law applicable to the case. 'Nul ne doit senrichir aux depens des autres ' No one ought to enrich himself at the expense of others. This doctrine at one stage of English common law was remedied by 'indebitatus assumpsit ' which action lay for money "had and received to the use of the plaintiff". It lay to recover 602 money paid under a mistake	 or extorted from the plaintiff by duress of his goods	 or paid to the defendant on a con sideration which totally tailed. On abolition of 'indebit atus assumpsit '	 courts used to imply a promise to pay which	 however	 in course of time was held to be purely fictitious. Lord Manslied in Moses vs Macferlan	 ; at 10 12 explained the juridical basis of the action for money "had and received" thus: "This kind of equitable action	 to recover back money	 which ought not in justice to be kept	 is very beneficial	 and therefore much encouraged. It lies only for money which	 'ex aequo et bono '	 the defendant ought to refund; it does not lie for money paid by the plain tiff	 which is claimed of him as payable in point of honour and honesty	 although it could not have been recovered from him by any course of law; as in payment of a debt barred by the Statute of Limitations	 or contracted during his infancy	 or to the extent of principal and legal interest upon a usurious contract	 or	 for money fairly lost at play; because in all these cases	 the defendant may retain it with a safe conscience	 though by positive law he was barred from recovering. But it lies for money paid by mistake; or upon a consideration which happens to fail; or for money got through imposition	 (express or implied); or extortion; or oppression; or an undue advan tage taken of the plaintiff 's situation	 contrary to laws made for the protection of persons under those circumstances. In one word	 the gist of this kind of action is	 that the defendant	 upon the circumstances of the case	 is obliged by the ties of natural jus tice and equity to refund the money." In that case Moses received from Jacob four promissory notes of cash each. He endorsed these to Macferlan who	 by a written agreement	 contracted that he would not hold Moses liable on the endorsement. Subsequently	 however	 Macferlan sued Moses on the notes in a Court of Conscience. The Court refused to recognise the agreement	 and Moses was forced to pay. Moses then brought an action against Macferlan in the king 's Bench for money "had and received" to his use. Lord Manslied allowed him to recover observing as above. Courts in England have since been trying to formulate a juridicial basis of this obligation. Idealistic formulations as 'aequum et bonum ' and 'natural justice ' were considered to be inadequate and the 603 more legalistic basis of unjust enrichment is formulated. The doctrine of 'unjust enrichment ' is that in certain situation it would be 'unjust ' to allow the defendant to retain a benefit at the plaintiff 's expense. The relatively modern principle of Restitution is of the nature of quasi contract. But the English law has not yet recognised any generalised right to restitution in every case of unjust enrichment. As Lord Diplock has said	 "there is no general doctrine of "unjust enrichment" recognised in English law. What it does is to provide specific remedies in particular cases of what might be classed as unjust enrichment in a legal system i.e. based upon the civil law. " In Sinclair vs Brougham	 Lord Haldane said that law could 'de jure ' impute promises to repay whether for money "had and received" otherwise	 which may	 if made defacto	 it would inexorably avoid. The principle of unjust enrichment requires: first	 that the defendant has been 'enriched ' by the receipt of a "benefit"; secondly	 that this enrichment is "at the expense of the plaintiff"; and thirdly	 that the retention of the enrichment be unjust. This justifies restitution. Enrichment may take the form of direct advantage to the recipient wealth such as by the receipt of money or indirect one for instance where inevitable expense has been saved. Another analysis of the obligation is of quasi contract. It was said; "if the defendant be under an obligation from the ties of natural justice	 to refund; the law implies a debt	 and give this action rounded in the equity of the plaintiff 's case	 as it were	 upon a contract (quasi ex contracts) as the Roman law expresses it." As Lord Wright in Fibrosa Spolka vs Fairbairn Lawson	 [1943] AC 32 1942 pointed out	 "the obligation is as efficacious as if it were upon a contract. Such remedies are quasi contract or restitution and theory of unjust enrichment has not been closed in English law. " Section 72 of the Indian Contract Act deals with liabil ity of person to whom money is paid or thing delivered	 by mistake or under coercion. It says: "A person to whom money has been paid	 or anything delivered	 by mistake or under coer cion	 must repay or return it." Illustration (b) to the section is: "A Railway Company refuses to deliver up certain goods to the consignee	 except upon the payment of an illegal 604 charge for carriage. The consignee pays the sum charged in order to obtain the goods. He is entitled to recover so much of the charge as was illegally excessive. " Our law having been codified	 we have to apply the law. It is true	 as Pollock wrote in 1905 in the preface to the first Edition of Pollock and Mulla 's Indian Contract and Specific Relief Acts: "The Indian Contract Act is in effect . . a code of English law. Like all codes based on an existing authoritative doctrine	 it assumes a certain knowledge of the principles and habits of thought which are embodied in that doctrine. " It is	 therefore	 helpful to know "those fundamental notions in the common law which are concisely declared	 with or	 without modification by the text. " There is no doubt that the instant suit is for refund of money paid by mistake and refusal to refund may result in unjust enrichment depending on the facts and circumstances of the case. It may be said that this court has referred to unjust enrichment in cases under section 72 of the Contract Act. See ; ; and ; The next question is whether	 and if so	 which provision of the will apply to such a suit. On this question we find two lines of decisions of this Court	 one in respect of civil sulks and the other in respect of peti tions under Article 226 of the Constitution of India. Though there is no constitutionally provided period of limitation for petitions under Article 226	 the limitation prescribed for such suits has been accepted as the guideline	 though little more latitude is available in the former. A tax paid under mistake of law is refundable under section 72 of the . In Sales Tax Officer vs Kanhaiya Lal	 where the respondent	 a regis tered firm	 paid sales tax in respect of the forward trans actions in pursuance of the assessment orders passed by the Sales Tax Officer for the year 1949 51; in 1952 the Allaha bad High Court held in M/s Budh Prakash Jai Prakash vs Sales Tax Officer	 Kanpur	 that the levy of sales tax on forward transactions was ultra vires. The respondent asked for a refund of the mounts paid	 filing a writ peti tion under Article 226 of 605 the Constitution. It was contended for the Sales Tax Author ities that the respondent was not entitled to a refund because (1) the amounts in dispute were paid by the respond ent under a mistake of law and were	 therefore	 irrecovera ble	 (2) the payments were in discharge of the liability under the Sales Tax Act and were voluntary payments without protest	 and (3) inasmuch as the monies which had been received by the Government had not been retained but had been spent away by it and the respondent was disentitled to recover the said amounts. This Court held that the term "mistake" in section 72 of the comprised within its scope a mistake of law as well as a mistake of fact and that	 under that section a party is entitled to recover money paid by mistake or under coercion	 and if it is established that the payment	 even though it be of a tax	 has been made by the party labouring under a mistake of law	 the party receiving the money is bound to repay or return it though it might have been paid voluntarily	 subject	 howev er	 to questions of estoppel	 waiver	 limitation or the like. On the question of limitation	 it was held that section 17(1)(c) of the would be applicable and that where a suit will be to recover "monies paid under a mistake of law	 a writ petition within the period of limita tion prescribed	 i.e.	 within 3 years ' of the knowledge of the mistake	 would also lie. " It was also accepted that the period of limitation does not begin to run until the plain tiff has discovered the mistake or could	 with reasonable diligence	 have discovered it. The money may not be recoverable if in paying and re ceiving it the parties were in pan delicto. In Kiriri Cotton Co. Ltd. vs Ranchhoddas Keshavji Dewani	 	 where the appellant company	 in consideration of granting to the respondent a sub lease asked for and received from him a premium of Sh. 10	000 and the latter.claimed refund thereof	 the Privy Council held that the duty of observing the law was firmly placed by the Ordinance on the shoulders of the landlord for the protection of the tenant	 and the appellant company and the respondent were not therefore in pari delic to in receiving and paying respectively the illegal premium	 which	 therefore	 in accordance with established common law principles	 the respondent was entitled to recover from the landlord and that the omission of a statutory remedy did not in cases of this kind exclude the remedy by money had and received. In the instant case also the parties could not be said to be in pari delicto in paying and receiving the extra 7 1/2% per cent. Had the appellants not paid this amount	 they would not have been given the contracts. In D. Cawasji &. Co. vs The State of Mysore & Anr. 	 ; 	 the appellants paid certain amount to the Government as 606 excise duty and education cess for the years 195 1 52 to 1965 66 in one case and from 1951 52 to 1961 62 in the other. The High Court struck down the provisions of the relevant Acts as unconstitutional. In Writ Petitions before the High Court claiming refund	 the appellants contended that the payments in question were made by them under mis take of law; that the mistake was discovered when the High Court struck down the provisions as unconstitutional and the petitions were	 therefore	 in time but the High Court dis missed them on the ground of inordinate delay. Dismissing the appeals	 this Court held that where a suit would lie to recover monies paid under a mistake of law	 a writ petition for refund of tax within the period of limitation would lie. For filing a writ petition to recover the money paid under a mistake of law the starting point of limitation is from the date on which the judgment declaring as void the particular law under which the tax was paid was rendered. It was held in D. Cawasji (supra) that although section 72 of the Contract Act has been held to cover cases of payment of money under a mistake of law	 as the State stands in a peculiar position in respect of taxes paid to it	 there are perhaps practical reasons for the law according different treatment both in the matter of the heads under which they could be recovered and the period of limitation for recovery. P.N. Bhagwati	 J.	 as he then was	 in Madras Port Trust vs Hymanshu Inter national	 	 deprecated any resort to plea of limitation by public authority to defeat just claim of citizens observing that though permissible under law	 such technical plea should only be taken when claim is not well founded. Section 17(1)(c) of the 	 provides that in the case of a suit for relief of the ground of mistake	 the period of limitation does not begin to run until the plaintiff had discovered the mistake or could with reasonable diligence	 have discovered it. In a case where payment has been made under a mistake of law as contrasted with a mistake of fact	 generally the mistake become known to the party only when a court makes a declaration as to the invalidity of the law. Though a party could	 with reasonable diligence	 discover a mistake of fact even before a court makes a pronouncement	 it is seldom that a person can	 even with reasonable diligence	 discover a mistake of law before a judgment adjudging the validity of the law. E.S. Venkataramiah	 J.	 as his Lordship then was	 in Shri Vallabh Glass Works Ltd. vs Union of India	 ; 	 where the appellants claimed refund of excess duty paid under Central Excise and Salt Act	 1944	 laid down that the excess amount paid by the appellants would have become refundable by virtue of section 72 of the 607 if the appellants had filed a suit within the period of limitation; and that section 17(1)(c) and Article 113 of the would be applicable. In Commissioner of Sales Tax	 U.P.v. M/s Auriaya Chamber of Commerce Allahabad; 	 	 the Supreme Court in its decision dated May 3	 1954 in Sales Tax Officer vs Budh Prakash Jai Prakash	 [1954] 5 STC 193 having held tax on forward contracts to be illegal and ultra vires the U.P. Sales Tax Act	 and that the decision was applicable to the assessee 's case	 the assessee filed several revisions for quashing the assessment order for the year 1949 50 and for subsequent years which were all dismissed on ground of limitation. In appeal to this Court Sabyasachi Mukharji	 J. while dismissing the appeal held that money paid under a mistake of law comes within mistake in section 72 of the Contract Act; there is no question of any estoppel when the mistake of law is common to both the assessee and taxing authority. His Lordship observed that section 5 of the Limitation Act	 1908 and Article 96 of its First Schedule which prescribed a period of 3 years were applicable to suits for refund of illegally collected tax. In Salonah Tea Co. Ltd. & Ors. vs Superintendent of Taxes	 Nowgong and Ors. 	 ; 	 the Assam Taxa tion (on Goods carried by Road or Inland Waterways) Act	 1954 was declared ultra vies the Constitution by the Supreme Court in Atiabari Tea Co. Ltd. vs State of Assam	 ; A subsequent Act was also declared ultra vires by High Court on August 1	 1963 against which the State of Assam and other respondents preferred appeals to Supreme Court. Meanwhile the Supreme Court in a writ petition Khyer bari Tea Co. Ltd. vs State of Assam	 ; 	 declared on December 13	 1963 the Act to be intra vires. Consequently the above appeals were allowed. Notices were	 therefore	 issued requiring the appellant under section 7(2) of the Act to submit returns. Returns were duly filed and assessment orders passed thereon. On July 10	 1973	 the Gauhati High Court in its Judgment in Loong Soong Tea Es tate 's case	 Civil Rule No. 1005 of 1969	 decided on July 10	 1973	 declared the assessment to be without jurisdic tion. In November	 1973 the appellant filed writ petition in the High Court contending that in view of the decision in Loong Soong Tea Estate 's case he came to know about the mistake in paying tax as per assessment order and also that he became entitled to refund of the amount paid. The High Court set aside the order and the notice of demand for tax under the Act but declined to order refund of the taxes paid by the appellant on the ground of delay and laches as in view of the High Court it was possible for the appellant to know about 608 the illegality of the tax sought to be imposed as early as in 1963	 when the Act in question was declared ultra vires. Allowing the assessee 's appeal	 Mukharji	 J. speaking for this Court held: "In this case indisputably it appears that tax was collected without the authority of law. Indeed the appellant had to pay the tax in view of the notices which were without juris diction. It appears that the assessment was made under section 9(3) of the Act. Therefore	 it was without jurisdiction. In the premises it is manifest that the respondents had no authority to retain the money collected with out the authority of law and as such the money was liable to refund. " The question there was whether in the application under article 226 of the Constitution	 the Court should have refused refund on ground of laches and delay	 the case of the appel lant having been that it was after the Judgment in the case of Loong Soong tea Estate	 the cause of action arose. That judgment was passed in July	 1973. The High Court was	 therefore	 held to have been in error in refusing to order refund on the ground that it was possible for the appellant to know about the legality of the tax sought to be imposed as early as 1973 when the Act in question was declared ultra vires. The Court observed: "Normally speaking in a society governed by rule of law taxes should be paid by citizens as soon as they are due in accordance with law. Equally	 as a corollary of the said statement of law it follows that taxes col lected without the authority of law as in this case from a citizen should be refunded because no State has the right to receive or to retain taxes or monies realised from citizens without the authority of law. " On the question of limitation referring to Suganmal vs State of M.P.	 AIR 1965 SC 1740	 and Tilokchand Motichand vs H.B. Munshi	 	 his Lordship observed that the period of limitation prescribed for recovery of money paid by mistake started from the date when the mistake was known. In that case knowledge was attributable from the date of the Judgment in Loong Soong Tea Estate 's case on July 10	 1973. There had been statement that the appellant came to know of that matter in October	 1973 and there was no denial of the averment made. On that ground	 the High Court was held to be in 609 error. It was accordingly held that the writ petition filed by the appellants were within the period of limitation prescribed under article 113 of the Schedule read with section 23 of the . It is thus a settled law that in suit for refund of money paid by mistake of law	 section 72 of the Contract Act is applicable and the period of limitation is three years as prescribed by Article 113 of the Schedule to the Indian and the provisions of section 17(1)(c) of that Act will be applicable so that the period will begin to run from the date of knowledge of the particular law	 where under the money was paid	 being declared void; and this court be the date of judgment of a competent court declaring that law void. In the instant case	 though the Madhya Pradesh High Court in Surajdin vs State of M.P.	 declared the collection on 7 1/2% per cent illegal and that decision was reported in 	 the Government was still charging it saying that the matter was under consideration of the Government. The final decision of the Government as stated in the letter dated 17.10. 1961 was purely an internal communication of the Government copy whereof was never communicated to the appellants or other liquor contractors. There could	 there fore	 be no question of the limitation starting from that date. Even with reasonable diligence	 as envisaged in section 17(1)(c) of the 	 the appellants would have taken at least week to know about it. Mr. Rana has fairly stated that there was nothing on record to show that the appellants knew about this letter on 17.10. 1961 itself or within a reasonable time thereafter. We are inclined to allow at least a week to the appellants under the above provision. Again Mr. Rana has not been in a position to show that the statement of the appellants that they knew about the mistake only after the judgment in Doongaji 's case reported in 	 in or about September	 1962	 whereafter they issued the notice under section 80 C.P.C. was untrue. This statement has not been shown to be false. In either of the above cases	 namely	 of knowledge one week after the letter dated 17.10. 1961 or in or about September	 1962	 the suit would be within the period of limitation under Article 113 of the Schedule to the . In the result	 we set aside the Judgment of the High Court	 allow the appeal and remand the suit. The records will be sent down forthwith to the trial court to decide the suit on merit in accordance with law	 expeditiously. The appellants shall be entitled to the costs of this appeal. R.N .J. Appeal allowed.

The appellant firm was allotted contracts for manufac ture and sale of liquor for the year 1959 and for the subse quent periods from 1.1. 1960 to 31.3.1961 for Rs.2	56	200 and Rs.4	71	900 respectively by the M.P. Govt. who also charged 7 1/2% over the auction money as mahua and fuel cess. As writ petitions challenging the government 's right to charge this 7 1/2% were pending in the M.P. High Court	 the Govt. announced that it would continue to charge it and the question of stopping it was under consideration of Govt. whose decision would be binding on the contractors. The appellant firm paid for the above contracts a total extra sum of Rs.54	606.00. On 24.4.1959 the M.P. High Court in Surajdin vs State of M.P.	 declared the collection of 7 1/2% as illegal. Even after this decision the Govt. continue to charge 7 1/2% extra money. Again on 31.8.1961	 the High Court of Madhya Pradesh in N.K. Doongaji vs Collector	 Surguja	 decided that charg ing of 7 1/2% by the Govt. above the auction money was illegal. Appellants came to know of this decision only in or about September	 1962. On 17.10.1964 the appellants gave a notice under section 80 C.P.C. to the Govt. of Madhya Pradesh requesting for the refund of Rs.54	606.00. failing which a suit for recovery would be filed and later they instituted a civil suit in the court of additional District Judge	 Jabalpur on 24.12.1964. The Govt. resisted the suit inter alia on the ground of limitation. The Trial Court held that the suit was barred by 597 limitation and dismissed it. The High Court also dismissed the appeal. The appellants then came up in appeal by special leave. While allowing the appeal and remanding the suit to the Trial Court for decision on merits. This Court	 HELD: 'Nul ne doit senrichir aux depens des autres ' No one ought to enrich himself at the expense of others. This doctrine at one stage of English common Law was remedied by 'indebitatus assumpsit ' which action lay for money ' had and received to the use of the plaintiff '. It lay to recover money paid under a mistake or extorted from the plaintiff by duress of his goods	 or paid to the defendant on a consider ation which totally failed. On abolition of 'indebitatus assumpsit '	 courts used to imply a promise to pay which	 however	 in course of time was held to be purely fictitious. [601G 602A] Courts is England have since been trying to formulate a juridical basis of this obligation. Idealistic formulations as 'aequum et bonum ' and 'natural justice ' were considered to be inadequate and the more legalistic basis of unjust enrichment is formulated. The doctrine of 'unjust enrich ment ' is that in certain situations it would be 'unjust ' to allow the defendant to retain a benefit at the plaintiff 's expense. The relatively modern principle of restitution is of the nature of quasi contract. But the English law has not yet recognised any generalised right to restriction in every case of unjust enrichment. [602H 603B] The principle of unjust enrichment requires; first	 that the defendant has been 'enriched ' by the receipt of a "benefit"; secondly. that this enrichment is "at the expense of the plaintiff" and thirdly	 that the retention of the enrichment be unjust. This justified restitution. Enrichment may take the form of direct advantage to the recipient wealth such as by the receipt of money or indirect one for instance where inevitable expense has been saved. [603C 603D] There is no doubt that the suit in the instant case	 is for refund of money paid by mistake and refusal to refund may result in unjust enrichment depending on the facts and circumstances of the case. [604D] Though there is no constitutionally provided period of limitation for petitions under Article 226	 the limitation prescribed for such suits has been accepted as the guide line	 though little more latitude is available in the for mer. [604F] For filing a writ petition to recover the money paid under a mis 598 take of law the starting point of limitation is three years is prescribed by Article 113 of the Schedule to the Indian and the provisions of section 17(1)(c) of the Act will be applicable so that the period will begin to run from the date of knowledge of the particular law	 where under the money was paid	 being declared void and this could be the date of the judgment of a competent court declaring that law void. [609B] Moses vs Macferlan	 ; at 1012; Sin clair vs Brougham	 ; Fibrosa Spolka vs Fair bairn Lawson; 	 = ; ; Sales Tax Officer vs Kanhaiya Lal	 ; M/s Budh Prakash Jai Prakash vs Sales Tax Officer	 Kanpur	 ; Kiriri Cotton Co. Ltd. vs Ranchhoddas Keshavji Dewani	 ; D. Cawasji & Co. vs The State of Mysore & Anr.	 ; ; Madras Port 7rust vs Hymanshu Inter national	 ; Shri Vallabh Glass Works Lid. vs Union of India; 	 ; Commissioner of Sales Tax	 U.P.v. M/s. Auriaya Chamber of Commerce Allahabad; 	 ; Sales Tax Officer vs Budh Prakash Jai Prakash	 [1954] 5 STC 193; Salonah Tea Co. Ltd. & Ors. vs Superin tendent of Taxes	 Nowgong & Ors. 	 ; ; Atiabari Tea Co. Ltd. vs State of Assam	 ; ; Khyerbari Tea Co. Ltd. vs State of Assam	 ; ; Loong Soong Tea Estate 's	 case decided on July 10	 1973; Suganmal vs State of M.P.	 AIR 1965 SC 1740; Tilokchand Motichand vs H.B. Munshi	 	 referred to.