Section 108(3A) of the Construction Act 1996 provides that qualifying construction contracts must include a clause permitting the adjudicator to correct a typographical or clerical error in their decision. These are often known as ‘slips’ hence the ‘Slip Rule’.
It is for the parties to agree any time limit upon the exercise of this power, otherwise the statutory Scheme for Construction Contracts requires that a correction under the slip rule must be made within 5 days of the decision.
The Act makes it clear that the power extends only to slips arising by accident or omission.
For example in Bloor Construction (UK) Ltd v Bowmer & Kirkland (London) Ltd  EWHC 183 (TCC) - the Adjudicator awarded a sum to the Claimant but in doing so failed to take into account payments already made by the Defendant. The Adjudicator revised his decision on the same day it was made. The Court allowed the adjudicator’s corrections meaning the Claimant could not enforce the original decision.
YCMS Ltd v Grabiner  EWHC 127 (TCC) – The Adjudicator made a mathematical error. However, instead of correcting the error, the adjudicator recalculated using different figures. The Court confirmed a simple correction would have fallen within the ambit of the slip rule, but that the Adjudicator’s decision to recalculate went beyond this, therefore, the revised award was invalid.
Dawnus Construction Holdings Ltd v Marsh Life Ltd  EWHC 1066 (TCC) – The Defendant failed to pay the monies awarded by the Adjudicator and instead invited the adjudicator to revise his decision under the slip rule. The Adjudicator declined. The Claimant then applied to enforce the decision arguing that, by inviting the adjudicator to correct the errors under the slip rule, the Defendant accepted the validity of the decision and made no general reservation of rights to challenge the decision. The Court agreed with this argument. If a party seeks to rely on the slip rule that party must also consider reserving its rights subsequently to challenge the enforcement of the award.
In conclusion, the slip rule is relatively narrow and is intended only to deal with a clerical or typographical error in expression or calculation rather than reasoning behind the Decision. It is essential parties review and check calculations in Adjudication Decisions promptly if they wish to rely on the Slip Rule to correct any such errors or omissions. In inviting the Adjudicator to exercise the Slip Rule care must be taken to preserve any subsequent jurisdictional challenge that party might wish to make.