The interaction between venture capital preference share structures and tax relief qualification thresholds has received comparatively little attention in Irish tax commentary despite its potentially significant practical consequences for founders and investor companies. This article considers whether cumulative redeemable convertible preference shares (CRCPS), including those commonly used by Enterprise Ireland (EI) and private investors, may constitute “ordinary shares” for the purposes of s597AA or “ordinary share capital” for the purposes of s626B of the Taxes Consolidation Act 1997 (TCA 1997). In particular, it examines how conversion rights, variable dividend mechanics and participation entitlements may unintentionally dilute founders and holding companies below the 5% thresholds required for revised entrepreneur relief and the holding company exemption. Drawing on Irish statutory provisions and persuasive UK authority, the article explores whether the legislation establishes a genuinely “bright dividing line” in assessing the extent of a person’s interest in the ordinary share capital of a company or whether, in practice, the classification is less certain.