since the clock cannot be turned back to re-measure the consumption, only estimates can be made, and if such estimate is not shown to be manifestly unreasonable, excessive or wrong, it may be accepted as proof upon a balance of probabilities of the amount estimated and claimed. [69] Despite the Defendant’s mere argument, the Defendant did not adduce any expert evidence or analysis to demonstrate that the Plaintiff’s back-billing calculation was excessive or inaccurate. The Defendant too, did not suggest any alternative method of calculation by calling any other expert to testify pertaining to this. [70] In that context, this Court finds guidance in Tenaga Nasional Bhd v. AWP Enterprise (M) Sdn Bhd [supra] wherein the Court of Appeal held: "[29] The appellant, upon whom the burden of proof lay to prove its case upon a balance of probabilities, having adduced evidence of the estimate and how it is arrived at, the burden shifts to the respondent to show that the estimate is in fact manifestly unreasonable, excessive or wrong." [71] Based on the above-quoted passage, it can be seen that the Court of Appeal affirmed that the initial burden lies with the Plaintiff in this case to establish its claim on a balance of probabilities, including evidence of how the estimate was derived. Once that burden is discharged, the evidential burden shifts to the Defendant to show that the estimate is manifestly unreasonable, excessive, or incorrect. In the present case, the Defendant failed to discharge that burden. [72] Therefore, there is no reason for this Court to reject the calculations made by PW3 which was subsequently approved by PW4. Unjust Enrichment [73] On the other hand, the Plaintiff in their submission asserted that the loss of revenue constituted unjust enrichment by the Defendant. Thus, having received the benefit of the electricity supply connected to the premise, the Defendant was liable to compensate the Plaintiff fairly and reasonably. [74] However so, the law on unjust enrichment is settled in Malaysia, especially on the cases involving claims by TNB in Ichi-Ban Plastic [supra]: [96] Coming back to the present appeals, as an alternative or in addition to the statutory cause of action under s.38(3) of the Act for recovery for loss of revenue, TNB is similarly entitled to legally pursue the claim based on a cause of action in unjust enrichment. If TNB elects to pursue relief for unjust enrichment then, as is a matter of settled law, there must be a proper and specific plea in the statement of claim that its cause of action is so founded. Further, material particulars that give rise to unjust enrichment must be provided in the pleadings. In this regard, it is a well-settled legal principle that the court should not decide on an issue that was not pleaded by the parties. Parties are required to set out the factual bases of their respective cases in the pleadings. The most important purpose of pleadings is to plead reasonable cause of action, define the issues of fact and questions of law to be determined by the court (see Saiman bin Umar v Lembaga Pertubuhan Peladang and another appeal [2015] 6 MLJ 492). Pleadings enable both parties to know in advance the averments being made against them so that they will not be taken by surprise during the trial. Tellingly, in the present appeals TNB did not plead that its cause of action was founded on the law of unjust enrichment. Unjust benefit was not a pleaded issue. With respect, the submission on the benefit/unjust enrichment question by learned counsel for TNB is, therefore, misconceived. [75] Bearing this in mind and also recognising that unjust enrichment is a form of restitution which shall be specifically pleaded by the Plaintiff as an alternative or in addition to the statutory cause of action under s.38(3) of the Act for recovery for loss of revenue, this Court wish not to decide on the issue which was found nowhere in the Plaintiff’s pleadings. Other Issues [76] To the Defendant’s defence in explaining the electricity consumption in his premise, he testified that the average electricity bill for the Defendant's premises was RM200 to RM500, be it before or after the inspection and rectification by the SEAL team, which was reasonable because in 2020 it was the implementation of the Movement Control Order (MCO) and that he spent his time at his medical shop from 07:30 am to 09:00 pm. [77] However, no documents were produced such as the shop's electricity bill to support his statement. As such, this Court hesitates in accepting that contention in whole. [78] Nonetheless, as explained earlier, the burden on the Plaintiff in this case is to prove that tampering was found on meter/meter installation at the Defendant’s premise regardless of whoever the perpetrator is. If this can be evinced (which this Court opines that the Plaintiff have), then it can be deduced that the Defendant, being the registered consumer have in fact benefitted from the electricity consumption at a lower price at the expense of the Plaintiff. [79] To put it simple, a consumer must pay for even the slightest of benefit he has received if the tampering is proven in his premise. This was encapsulated in Thomas Thomas V. Tenaga Nasional Bhd [supra] as such: [16] Meter tampering, causing damage to meter or dishonest consumption of electricity are strictly criminal matters which do not and cannot affect TNB's right to recover loss of revenue by way of civil proceedings pursuant to s. 38(3) to (5). No registered consumer can walk away without paying anything to TNB on the ground that the meter had been damaged or tampered with without his knowledge. [17] In our view, in an action by TNB to recover loss of revenue resulting from meter tampering, a registered consumer cannot avail himself of such defence for the simple reason that it will result in unjust enrichment to the consumer. He can only be absolved of liability if he can show that no electricity was consumed at the premises during the period that the meter was tampered with. [18] It is not open to the appellant to say that he did not "benefit" from the consumption of the electricity on the ground that the premises had been "continuously occupied by an unbroken chain of tenants". The simple truth is, the premises belonged to him and he was the registered consumer under account No. 012364675401. Section 71 of the Contracts Act 1950 therefore comes into play. ……. [20] Therefore, as far as consumption of electricity in the premises is concerned, it was the appellant's sole responsibility, being the "consumer" under the agreement, to pay all outstanding charges due to TNB. On the evidence as found by the learned Sessions Court Judge and as affirmed by the learned High Court Judge on appeal, electricity had in fact been consumed during the period from 22 September 2004 to 21 December 2007. It is irrelevant who actually consumed the electricity. [21] As TNB's registered consumer, it was the appellant's responsibility to ensure that the meter at the premises was not damaged or tampered with. This responsibility remains with the appellant throughout the duration of the agreement unless by his tenancy agreement with the tenant, he had assigned such responsibility to the tenant. Even then such agreement would not bind TNB, not being a party to the tenancy agreement. [22] Thus, where the meter was damaged or tampered with by the tenant or the occupier with or without the appellant's permission or by anyone else during the agreement period, the appellant must pay for the resulting loss of revenue suffered by TNB, not because he had anything to do with the tampering or damage caused to the meter but because he was bound by agreement to pay for the electricity charges. The loss of revenue under such circumstances cannot fall on TNB's head. That will be grossly unfair to TNB. [80] Other than that, the Defendant’s rebuttal to the Plaintiff’s claim was nothing more than bare denial. The Defendant’s defence, be it in his pleadings or in his testimony, was a bare denial where he denied any knowledge on the Plaintiffs’ assertions, including the outcome of the inspection and the existence of the tampering of the meter/meter installation. [81] Without any convincing or corroborative evidences produced, this Court believes that the object of the defence cannot be achieved by a mere general denial which do not constitute a defence to the claim, more so when the burden shifted to the Defendant to rebut [the Plaintiff’s claim] that the meter was not at all tampered. [82] Overall, this Court believes that the Defendant have indeed benefitted from the tampering found at the meter/meter installation at his premise. Thus, denying the Plaintiff’s right (or in specific, statutory right) under the ESA 1990 would mean that the Defendant will not be required to pay for the energy consumed by him and that could not be tolerated by this Court. [83] Furthermore, this Court reckon that the Plaintiff’s total loss of revenue was properly quantified. [84] Therefore, given that the Plaintiff’s calculation followed a legally accepted method, and the Defendant failed to provide any alternative calculation, this Court finds no reason not to accept the amount arrived at by the Plaintiff in full. Whether the Plaintiff's Claim or a Substantial Part of the Plaintiff's Claim is Time-barred Under the Limitation Act 1953 [85] The Court now deals with the Defendant’s contention in their pleading that the Plaintiff's claim is time-barred under the Limitation Act 1953 (LA 1953). Although it can be observed that this issue was dealt with in their submission, this Court steps in to clarify this issue nonetheless for the sake of completeness and as the matter is included in the Parties’ issues to be tried. [86] The answer to this can be distinctly found under S.6(1) of the LA 1953 and in the case of Evergrowth Aquaculture Sdn Bhd [supra] as such: [78] Learned counsel for the respondents submitted that TNB’s cause of action starts to run from the date the meter was alleged to have been first tampered with and not from the meter tampering was alleged to have been discovered. According to learned counsel, subsection 38(3) of the ESA 1990 provides that TNB is entitled to claim for loss of revenue due to the “offence committed” under subsection 37(1), (3) or