Legal Principles Governing the Application of the Slip Rule
22Pursuant to r 36.17 of the UCPR, the Court has the power to correct any error arising from an accidental slip or omission in a judgment or order ("the slip rule"). The rule provides that:
36.17 Correction of judgment or order ("slip rule")
If there is a clerical mistake, or an error arising from an accidental slip or omission, in a judgment or order, or in a certificate, the court, on the application of any party or of its own motion, may, at any time, correct the mistake or error.
23Traditionally, the authorities have described the rule as applying to the correction of clerical errors or accidental omissions or slips, that is to say, mistakes upon which no real difference of opinion can exist and upon which no further exercise of a court's discretion is required. It does not confer power to supplement or vary final orders by making substantive alterations to determine points that were not argued, considered or decided at the hearing.
24Thus in Storey & Keers Pty Ltd v Johnstone (1987) 9 NSWLR 446 McHugh JA stated the following in relation to the slip rule and the jurisdiction of the Court to correct accidental slips or omissions (at 449E-G):
The Courts of Common Law and the Court of Chancery had inherent power to correct any clerical mistake or error in a judgment or order if it was the result of an accidental slip or omission: Lawrie v Lees (1881) 7 App Cas 19 at 34-35. This power was an exception to the general principle that a party is bound by judgment or order once it has been drawn up unless he can set it aside: Kinch v Walcott [1929] AC 482. But although the principle of the slip rule is clear enough in conception, its application in practice has often proved difficult. The dividing line between a mistake or error which Is the result of an accidental slip or omission and a mistake or error which is the difficulty became much greater when it was decided that an error might be the result of an accidental slip or omission even though, because of the inadvertence of the party's legal representative, the point was not raised at the hearing of the action: cf L Shaddock & Associates Pty Ltd v Parramatta City Council [No 2] (1982) 151 CLR 590 at 594-595.
25In that decision his Honour further opined that the rationale of the slip rule as requiring (at 453E):
...that an omission or mistake should not be treated as accidental if the proposed amendment requires the exercise of an independent discretion or is a matter upon which a real difference of opinion might exist ... In general the test of whether a mistake or omission is accidental is that applied by Lord Herschell in Hatton v Harris [1892] AC 547 (at 588) if the matter had been drawn to the court's attention would the correction at once have been made?
26But the scope of the slip rule was more recently considered by the Court of Appeal in Newmont Yandal Operations Pty Ltd v The J Aron Corporation and The Goldman Sachs Group Inc [2007] NSWCA 195; (2007) 70 NSWLR 411. In particular, the common law rule was assessed in light of the promulgation of s 56 of the CPA, or 'the overriding purpose rule'.
27In Newmont Yandal the Court of Appeal observed that caution must be exercised in the application of case law from the past or from other jurisdictions when applying the slip rule in a modern context because of the enactment of s 56 (at [26]-[27]):
26. Accordingly, this Court, unlike other courts which have the traditional form of slip rule, is required to approach the task of interpreting the relevant words, including "error", "accidental slip or omission" and "correct", in such a manner as to give effect to the overriding purpose. Such an interpretive requirement may lead to different results in New South Wales when compared with the past or with other jurisdictions.
27. Similarly, the Court must seek to give effect to the overriding purpose when exercising the discretion to correct an error or mistake in a judgment or order pursuant to r 36.17. In each respect this constitutes a substantive difference, which requires the Court to treat prior case law and the case law from other jurisdictions with some care.
28In Newmont Yandal Spigelman CJ noted that what constitutes an 'error' that is suitable for correction under the slip rule remains somewhat elusive (at [23]):
... There is a substantial body of case law about whether or not a particular "slip or omission" was "accidental". There is a more limited body of case law on what constitutes an "error" and what is a permissible "correction". It is, of course, important that the Court apply the actual formulation in the rule. Many of the cases, for example those which state that a "deliberate" decision is not within the rule, can be understood as a way of expressing the proposition that the act or omission there relied upon was not "accidental".
29Hence if a judge "assesses the evidence wrongly or misconstrues or misappreciates the law, the resulting award or judgment will be erroneous but it cannot be corrected ... The remedy is to appeal" (Mutual Shipping Corp of New York v Bayshore Shipping Co of Monrovia [1985] 1 All ER 520 at 530 per Donaldson MR, quoted in George v Webb [2012] NSWSC 86 per Ward J at [23]).
30But after reviewing the authorities, the Court of Appeal in Newmont Yandal held that by reason of the insertion of the overriding purpose rule into the CPA, the slip rule may be applied to carry into effect the actual intention of the judge making the order to ensure that the order does not have a consequence which the judge clearly intended to avoid (at [116]). As a result, orders may be corrected under this rule to avoid or ameliorate "an unforeseen and unintended legal consequence" (at [58] and [60]).
31The relevant intention is the objective intention of the decision-maker at the time the original orders were made (George v Webb [2012] NSWSC 86 per Ward J at [26] and El Boustani v Minister Administering the Environmental Planning and Assessment Act 1979 (No 2) [2013] NSWLEC 25 at [12]).