In a recent case before a Scottish court, an adjudicator made a mistake in the calculations in his decision (NKT Cables A/S v SP Power Systems Limited). One of the parties pointed this out and the adjudicator promptly issued an amended decision, correcting the error and including two items previously omitted from the calculations.

The slip rule introduced in the amended Scheme for Construction Contracts (both in England and Wales and in Scotland) allows for the correction of "a clerical or typographical error arising by accident or omission", but the court ruled that it did not apply in this case. However, could a similar slip rule be implied and, if so, would it permit the inclusion of the items that had been left out?

On the basis that there might be scope for implication of a term similar to the amended scheme slip rule, the court decided that it would not apply to the inclusion of the originally omitted items. It noted that the rule's scope is relatively narrow and is not directed to pure omissions. A "clerical or typographical" error indicates an error in expression or calculation of something in the decision, not an error relating to the reason or intention forming the basis of that decision. Further, "accident or omission" suggests the correction of slips or mistakes in expression, rather than changes to the reasoned or intended basis of the decision. If the slip rule allowed the correction of pure omissions, or gave effect to second rather than first thoughts or intentions, it could seriously undermine the interim finality of scheme adjudications.

The court also found that the adjudicator had addressed only one of the substantive defences, and had therefore failed to exhaust his jurisdiction in respect of these. This failure was material as each defence afforded a complete defence to the relevant claim, making the decision (or, if severable, the relevant parts thereof) unenforceable.

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