Amendments to Airport Cost of Capital IMs – equity beta
We are considering potential amendments to aspects of the Airport Input Methodologies for cost of capital.
The amendments we are considering are to the equity beta – one of the fixed Weighted Average Cost of Capital (WACC) parameters – in light of issues that were identified in the R Code that informed the Commission’s final decisions on cost of capital in the 2023 IM Review.
Background
In late December 2025, the High Court released its judgment on appeals brought by the New Zealand Airports Association Incorporated and Auckland, Wellington and Christchurch International Airports. The appeals challenged the 2023 changes to the Input Methodology rules for airports. The Court declined the appeals and found in the Commission’s favour on all three grounds.
This judgement supports our role in providing clarity and certainty around the rules governing airport pricing, service quality and transparency. During the appeals process, we committed to considering whether amendments are needed to address technical errors that the airports had identified in the R code underpinning aspects of the equity beta parameter.
Proposed time frames for this amendment
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Draft decision by the Commission |
March 2026 |
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Submissions due on draft IM amendment decision |
April 2026 |
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Cross-submissions due on draft IM amendment decision |
May 2026 |
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Final decision by the Commission on IM amendments |
June 2026 |
Updates and any refinements to our process steps and timelines will be published here.