In 2012 the New Zealand Financial Markets Authority (FMA) introduced guidelines for the disclosure of non‐GAAP financial information. This study investigates the effect of those guidelines on New Zealand listed companies. The findings show that, despite not being mandatory, these guidelines are modifying corporate disclosure behaviour. Companies have improved the way in which they disclose non‐GAAP earnings information and there has been a reduction in the emphasis given to non‐GAAP earnings compared with the emphasis given to audited statutory profit. However, the study also highlights areas for improvement, including the depth of explanation of non‐GAAP earnings calculations and adjustments, and concern about multiple adjusted earnings figures to explain performance.