The limitation period for recovering debts must be calculated from the discovery of an error, and amendments to regulation do not apply retrospectively if they impair pre-existing rights.

[1] The background facts of this appeal against the concurrent findings of the courts below could be summarised as follows.

[2] At all material times, the appellant was a national electricity supplier whilst the respondent was its customer. Sometime in 1996, the respondent successfully applied to the appellant for the supply of electricity to be upgraded from 610kW to 1210kW. On 15 August 1996, the parties entered into a fresh contract for the supply of electricity. It was not in dispute that after the upgrade of the supply, the respondent duly paid all electricity bills without fail, as and when issued. In January 2003, the appellant "discovered" that the respondent had been undercharged for a period of [73] months, that is, from October 1996 to October 2002, due entirely to the application of a wrong meter multiplying constant (multiplier) by the appellant. The correct multiplier should have been 100 instead of 50. By reason of the application of the wrong multiplier, the respondent was undercharged a total of RM581,876.77 (shortfall). On 15 November 2002, the multiplier was corrected to 100. Since then, the respondent had settled all electricity charges calculated on a multiplier of 100. Meantime, further to the discovery of the wrong multiplier, the appellant issued two demands, on 13 January 2003 and 29 July 2003, to the respondent to settle the shortfall. On 15 September 2003 (see 158AR), the respondent sought indulgence from the appellant to pay a reduced sum (RM28,328.40) by ten instalments. But that application was rejected by the appellant who proceeded to file action, on 26 October 2005, to recover the shortfall.

[3] On the issue of limitation, the trial court held (i) that s 29 of the Limitation Act 1953 (Act) applied and that time only started to run when the mistake in the multiplier was discovered, (ii) that by reason of reg 11(2) of the Licensee Supply Regulations 1990, post amendment, which proviso reads "that the period for any retrospective adjustment shall not exceed three months from the date the consumer has been informed about being undercharged or overcharged", which came into effect on 15 December 2002, a retrospective adjustment of a customer's account could not exceed three months, (iii) that the cause of action arose after the amendment to reg 11(2) (see p 9 of the grounds of the trial court at p 34 of the Appeal Record), and (iv) that the appellant could not recover a retrospective adjustment of more than three months. The trial court dismissed the claim. The court of Appeal agreed with the trial court.

[4] Being aggrieved, the appellant applied and obtained leave on 11 September 2012, to appeal against the decision of the court of Appeal in respect of the matter decided by the trial court in the exercise of its original jurisdiction, on the following two "questions of law":

"Whether reg 11(2) of the Licensee Supply Regulations 1990, post amendment in 2002, has retrospective effect?"

"Whether reg 11(2) of the Licensee Supply Regulations 1990, which came into operation on 15 December 2002 applies to a cause of action that arose before the year 2002?"

[5] Before us, learned counsel for the appellant submitted that both leave questions should be answered in the negative. Learned counsel for the respondent agreed that reg 11(2), post amendment, had no retrospective effect. It would seem that both parties knew what should be the answer to the 1st leave question, which should free us to proceed to the next leave question. Still, we could take this opportunity to uphold that it is indeed a rule of construction that a statute should not be interpreted retrospectively to impair an existing right or obligation, unless such a result is unavoidable by reason of the language used in the statute (Yew Bon Tew & Anor v. Kenderaan Bas Mara, 1983 MarsdenLR 26 ; per Lord Brightman, deliver