In adjudications, the ‘slip rule’, as many of you will recall, is a rule under the Scheme for Construction Contracts which permits an adjudicator to correct a clerical or typographical error arising by an accident or omission, within a short period after publishing a decision.

A recent case in Scotland* (where the rule currently applies) has decided that the slip rule did not apply in the specific circumstances where an adjudicator amended his decision by including two items which had previously not been referred to in his original decision.


A cable supplier (NKT) obtained a decision in its favour on 1 July 2016. On 4 July, NKT emailed the adjudicator querying his decision as it claimed that he had not accurately accounted for his working out of the gross value of the contract. The adjudicator shortly replied accepting that he had made an error and he submitted a revised decision which crucially included two omitted items.  He then revised the total sum awarded in his decision. The responding party (SP) was copied into the email correspondence between the adjudicator and NKT, however, as the emails were sent late at night after business hours, SP did not respond until the next morning after the adjudicator had already issued his revised decision.

SP submitted that the adjudicator had acted outside his jurisdiction and had no power to amend his original decision, and that the correction was not within the scope of the slip rule, whether by implication or under the Scheme for Construction Contracts.


The court held that the amendments introduced by the Scheme for Construction Contracts (Scotland) Amendment Regulations 2011, including the slip rule, did not apply to the contract in question as this contract dated back to 2010 and the rule only applied to contracts post-dating the Regulations coming into force. The court then considered whether, instead,  there was an implied slip rule that could apply in this case.

The court held that no slip rule applied in this case, as it was only intended to cover clerical and typographical errors.  What the adjudicator had changed in his amended decision was outside of any slip rule as he sought to correct an error which was a true omission (not a typographical error). Neither of the two items added to the amended decision were referred to in the original decision or in the calculation of the sum due to NKT.  The court decided that the adjudicator had sought to “correct” an error which was actually an omission which elated to the reasoning or intention behind his decision, rather than correcting a mistake. For these reasons, what the adjudicator had purported to do was outside the scope of any slip rule.


This case is a useful reminder of the circumstances in which the slip rule applies; that an implied slip rule may be incorporated into a contract even if it re-dates the amendment introducing the slip rule under the Scheme. However, its operation will only apply to true clerical or typographical errors and is not to be used to rectify omissions in the decision.

This blog post was written by Gemma Wilson. For further information, please contact:

Gemma Wilson, associate, Construction

T: 0161 836 7884


* NKT Cables A/S v SP Power Systems Limited (2017)





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This blog is intended only as a synopsis of certain recent developments. If any matter referred to in this blog is sought to be relied upon, further advice should be obtained.