The fine is the most common penalty imposed by courts of summary jurisdiction in Australia, and fines imposed by way of penalty notice or infringement notice are a multiple of those imposed by the courts. The latter are being used for an increasing range of offences. This progressive ‘monetization of justice’ (O’Malley) and its effects have passed largely unnoticed. The enforcement of fines has, in most parts of Australia, been passed from the justice system to government revenue agencies with barely any public scrutiny or academic analysis. Sentencing councils, law reform commissions and audit and ombudsman offices have completed inquiries on fines, some of them wide-ranging and highly critical of existing arrangements. Yet, these inquiries arouse little public or media interest and, partly in consequence, there has been little political will to tackle fundamental problems as distinct from tinkering at the margins. After surveying the theoretical literature on the role of the fine, this paper considers the neglected question of fines enforcement. We present three case studies from different Australian jurisdictions to highlight issues associated with different models of enforcement. We show that fines enforcement produces very real, but often hidden, hardships for the most vulnerable. Despite its familiarity and apparent simplicity and transparency, the fine is a mode of punishment that hides complex penal and social realities and effects.