Where the court is asked to allow rectification of a pension scheme deed, the "convincing proof" of the parties' intentions need only be assessed on the balance of probabilities according to the decision of the Supreme Court of Ireland in Boliden Tara Mines Limited v Cosgrove and Others [2010] IESC 62.

This case related to the Tara Mines Pension Plan. In 1999, the principal employer of the Plan agreed several benefit improvements in return for general cost savings and increases in productivity. One such improvement was the removal of "integration" with the Irish state pension for all active members of the Plan as at 20 February 1988 ("integration" permitted deductions to be made from employees' salary to reflect state pension payments). The definition of "pensionable salary" was amended by deed to reflect this change.

Although the parties intended that the change should apply to active members only, the amended definition of "pensionable salary" was drafted widely and inadvertently applied to members of a separate plan set up specifically for former employees who had stopped work because of ill-health or disability. Although these members were technically active members of the Plan, it was never intended that they should benefit from the removal of integration and the principal employer applied to the High Court to obtain rectification of the deed of amendment on that basis.

The employer's claim was rejected by the High Court on the basis that it had failed to provide clear and convincing evidence of common intention. On appeal, the Supreme Court reversed this decision and permitted rectification on the basis that there was "ample evidence" of common intention on the part of the employer and the trustee.

The Court commented that the high standard adopted by the judge at first instance, though commendable, almost approached the standard used in criminal proceedings ("beyond reasonable doubt"), which was not appropriate in the circumstances. It reiterated that the correct standard of proof in civil cases such as this was the balance of probabilities, and not the higher standard put forward by the judge at first instance.

Comment: As this is an Irish case, it is not binding although the guidance it gives about the circumstances in which rectification will be granted is instructive. Although it acknowledges that it is not necessary to prove the parties' common intentions "beyond reasonable doubt", strong evidence of agreement will still be required to found a successful case for rectification.